Method and apparatus for detecting optical fiber link, and optical fiber communication system

Abstract

The application discloses a detection method and device of an optical fiber link and an optical fiber communication system, and belongs to the technical field of communication. An optical sending device sends a first optical signal to an optical receiving device through an optical fiber link, the first optical signal carries a detection sequence, the detection sequence comprises a plurality of sub-detection sequences, and the plurality of sub-detection sequences are carried in the first optical signal in a multiplexing manner. The optical receiving device receives a second optical signal through the optical fiber link, the second optical signal comprises the first optical signal and a reflected optical signal. The optical receiving device demodulates the second optical signal to obtain the detection sequence. The optical receiving device determines the transmission performance of the optical fiber link according to the demodulated detection sequence. The application utilizes the existing optical sending device and the optical receiving device of the optical fiber communication system to detect the transmission performance of the optical fiber link, and the detection of the optical fiber link can be realized without deploying additional devices in the optical fiber link, the hardware implementation of the detection of the optical fiber link is simple, and the detection cost is low.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to a method and apparatus for detecting optical fiber links and an optical fiber communication system. Background Technology

[0002] Fiber optic communication systems typically consist of optical transmitting equipment, optical receiving equipment, and fiber optic links. The optical transmitting and receiving equipment are connected via a fiber optic link. The optical transmitting equipment modulates the information to be transmitted onto an optical signal and then transmits this signal to the optical receiving equipment via the fiber optic link. The optical receiving equipment receives the optical signal via the fiber optic link and demodulates the information carried by the signal. Fiber optic link anomalies can cause multipath interference (MPI) noise, mode partition noise (MPN), etc., leading to a deterioration in the signal-to-noise ratio (SNR) of the optical signal received by the optical receiving equipment. Therefore, it is necessary to test the transmission performance of the fiber optic link.

[0003] Currently, optical time domain reflectometers (OTDRs) are commonly used to detect the transmission performance of fiber optic links. For example, an OTDR is deployed in a fiber optic link, controlling it to transmit optical signals through the link and detect the reflected optical signals. The transmission performance of the fiber optic link is determined based on the reflected optical signals detected by the OTDR.

[0004] However, currently, testing fiber optic links requires an additional OTDR, which makes the hardware implementation for testing the transmission performance of fiber optic links complex and the testing cost high. Summary of the Invention

[0005] This application provides a method and apparatus for detecting optical fiber links, and an optical fiber communication system. The technical solution of this application is as follows.

[0006] Firstly, a method for detecting an optical fiber link is provided, applied to an optical transmitting device. The method includes: generating a first optical signal carrying a detection sequence for use by an optical receiving device to detect the transmission performance of the optical fiber link; the detection sequence comprising multiple sub-detection sequences carried in the first optical signal in a multiplexed manner; transmitting the first optical signal to the optical receiving device via the optical fiber link; the first optical signal becoming a second optical signal after transmission through the optical fiber link between the optical transmitting device and the optical receiving device; the second optical signal comprising the first optical signal and a reflected optical signal. The reflected optical signal is an optical signal generated by reflection of the first optical signal within the optical fiber link. For example, the reflected optical signal is an optical signal generated by multiple (e.g., an even number of) reflections of the first optical signal between reflection points on the optical fiber link, including connectors, the end face of a laser in the optical transmitting device, etc. The intensity of the reflected optical signal depends on the reflection intensity of the reflection points.

[0007] The technical solution provided in this application involves an optical transmitting device transmitting a first optical signal carrying a detection sequence through an optical fiber link between the transmitting device and an optical receiving device. The first optical signal is transformed into a second optical signal after transmission through the optical fiber link. After receiving the second optical signal, the optical receiving device can determine the transmission performance of the optical fiber link based on the detection sequence carried by the second optical signal. Therefore, this application utilizes existing optical transmitting and receiving devices in an optical fiber communication system to detect the transmission performance of an optical fiber link. It eliminates the need for additional equipment such as an OTDR in the optical fiber link to perform the detection, resulting in simple hardware implementation and low detection costs.

[0008] Optionally, the multiplexing method includes any of the following: wavelength division multiplexing, parallel fiber multiplexing, or time division multiplexing.

[0009] Optionally, the multiplexing method is wavelength division multiplexing (WDM). The first optical signal includes multiple sub-optical signals, each corresponding one-to-one with a multiple sub-detection sequence. Any two sub-optical signals have different wavelengths (i.e., the wavelengths of the multiple sub-optical signals are all different). The optical fiber link includes a first optical fiber used to transmit the multiple sub-optical signals. For example, the first optical signal is obtained by multiplexing the multiple sub-optical signals using an optical transmitting device, and the first optical fiber is used to transmit the first optical signal for transmitting the multiple sub-optical signals.

[0010] The technical solution provided in this application, in the wavelength division multiplexing (WDM) method, uses a first optical fiber to transmit multiple sub-optical signals including the first optical signal. Therefore, the WDM method helps to save optical fiber resources, and the benefits of applying the WDM method in long-distance optical fiber communication systems are significant.

[0011] Optionally, the multiplexing method is a parallel fiber multiplexing method; the first optical signal includes multiple sub-optical signals, each corresponding one-to-one with a multiple sub-detection sequence; the optical fiber link includes a first optical fiber and a second optical fiber in parallel, the first optical fiber being used to transmit the first sub-optical signal, and the second optical fiber being used to transmit the second sub-optical signal, the multiple sub-optical signals including the first sub-optical signal and the second sub-optical signal. For example, the optical fiber link includes multiple parallel optical fibers, each corresponding one-to-one with a multiple sub-optical signal, each fiber being used to transmit its corresponding sub-optical signal.

[0012] The technical solution provided in this application uses multiple parallel optical fibers to transmit multiple sub-optical signals included in the first optical signal in a one-to-one correspondence in the parallel fiber multiplexing method. Therefore, the parallel fiber multiplexing method requires relatively more optical fiber resources and is usually used in short-distance optical fiber communication systems.

[0013] Optionally, the first and second optical fibers satisfy the following conditions: the lengths of the first and second optical fibers are the same; and the positions of the connectors on the first and second optical fibers are the same. For example, the first and second optical fibers are encapsulated in the same optical cable, and the connectors on the first and second optical fibers are multiple-fiber push-on / pull-off (MPO) connectors on the optical cable.

[0014] The technical solution provided in this application, because the lengths of the first and second optical fibers are the same, and the positions of the connectors on the first and second optical fibers are also the same, means that the influence of the first optical fiber on the first sub-optical signal is the same as the influence of the second optical fiber on the second sub-optical signal. This facilitates the joint detection of the transmission performance of the optical fiber link using the sub-detection sequences carried by the first and second sub-optical signals. For example, if the first and second optical fibers are encapsulated in the same optical cable, the same MPO connector on this cable has the same influence on both fibers, thus having the same influence on the first sub-optical signal transmitted in the first fiber and the second sub-optical signal transmitted in the second fiber. The first and second sub-optical signals experience the same physical environment during transmission. Furthermore, encapsulating the first and second optical fibers in the same optical cable improves the integration of the optical fiber link and facilitates its deployment and connection.

[0015] Optionally, the plurality of sub-detection sequences include a first sub-detection sequence, and the plurality of sub-optical signals include a first sub-optical signal. The first sub-optical signal corresponds to the first sub-detection sequence, and the first sub-optical signal carries a plurality of first sub-detection sequences, which are periodically distributed in the first sub-optical signal. There are boundary markers between adjacent first sub-detection sequences among the plurality of first sub-detection sequences; or, adjacent first sub-detection sequences among the plurality of first sub-detection sequences are consecutive. The first sub-detection sequence can be any one of the plurality of sub-detection sequences, and the first sub-optical signal is used to carry the first sub-detection sequence. After transmission via the optical fiber link, the first sub-optical signal becomes a third sub-optical signal, which includes the first sub-optical signal and a first sub-reflected optical signal. The second optical signal includes the third sub-optical signal, and the reflected optical signal includes the first sub-reflected optical signal. The first sub-reflected optical signal is the optical signal generated by the reflection of the first sub-optical signal in the optical fiber link.

[0016] The technical solution provided in this application involves a first sub-optical signal carrying a plurality of periodically distributed first sub-detection sequences (correspondingly, a third sub-optical signal also carries a plurality of periodically distributed first sub-detection sequences). This facilitates the optical receiving device in demodulating the first sub-detection sequences from the third sub-optical signal, thereby determining the transmission performance of the optical fiber link based on the demodulated first sub-detection sequences. For example, if the first sub-optical signal carries only one first sub-detection sequence (correspondingly, the third sub-optical signal also carries only one first sub-detection sequence), the optical receiving device needs to accurately demodulate this first sub-detection sequence from the third sub-optical signal in order to determine the transmission performance of the optical fiber link based on the demodulated first sub-detection sequence. However, if the first sub-optical signal carries a plurality of periodically distributed first sub-detection sequences (correspondingly, the third sub-optical signal also carries a plurality of periodically distributed first sub-detection sequences), the optical receiving device only needs to be able to demodulate any one of these plurality of first sub-detection sequences from the third sub-optical signal to determine the transmission performance of the optical fiber link based on the demodulated first sub-detection sequence. This reduces the difficulty for the optical receiving device to demodulate the first sub-detection sequence from the third sub-optical signal. Furthermore, if there are boundary markers between adjacent first sub-detection sequences carried by the first sub-optical signal, there are also boundary markers between adjacent first sub-detection sequences carried by the third sub-optical signal. The optical receiving device can determine (i.e., identify) the first sub-detection sequence carried by the third sub-optical signal based on the boundary markers carried by the third sub-optical signal, further reducing the difficulty for the optical receiving device to identify the first sub-detection sequence from the third sub-optical signal.

[0017] Optionally, the multiplexing method is time-division multiplexing; the first optical signal carries a first sub-detection sequence in a first time period, and the first optical signal carries a second sub-detection sequence in a second time period. The plurality of sub-detection sequences includes the first sub-detection sequence and the second sub-detection sequence. The first sub-detection sequence and the second sub-detection sequence can be any two of the plurality of sub-detection sequences. For example, the plurality of sub-detection sequences correspond one-to-one with multiple time periods, and the first optical signal carries the corresponding sub-detection sequence in each of the plurality of time periods.

[0018] Optionally, the first optical signal carries multiple first sub-detection sequences in the first time period, and the multiple first sub-detection sequences are periodically distributed in the first optical signal; there are boundary markers between adjacent first sub-detection sequences among the multiple first sub-detection sequences; or, adjacent first sub-detection sequences among the multiple first sub-detection sequences are continuous.

[0019] The technical solution provided in this application involves a first optical signal carrying multiple periodically distributed first sub-detection sequences in a first time period (correspondingly, a second optical signal also carries multiple periodically distributed first sub-detection sequences). This facilitates the optical receiving device in demodulating the first sub-detection sequences from the second optical signal, and then determining the transmission performance of the optical fiber link based on the demodulated first sub-detection sequences from the second optical signal. Furthermore, when there are boundary markers between adjacent first sub-detection sequences carried by the first optical signal (correspondingly, there are also boundary markers between adjacent first sub-detection sequences carried by the second optical signal), the optical receiving device can determine (i.e., identify) the first sub-detection sequences carried by the second optical signal based on the boundary markers carried by the second optical signal, reducing the difficulty for the optical receiving device to identify the first sub-detection sequences from the second optical signal.

[0020] Optionally, the first optical signal also carries a data signal. That is, the first optical signal carries a detection sequence and a data signal. For example, the first optical signal includes multiple sub-optical signals, which correspond one-to-one with multiple sub-detection sequences. Each sub-optical signal carries a corresponding sub-detection sequence, and at least one of the multiple sub-optical signals carries a data signal. The data signals carried by different sub-optical signals can be different.

[0021] The technical solution provided in this application carries a data signal and a detection sequence for detecting the transmission performance of the optical fiber link in the first optical signal, which can realize the in-path detection of the transmission performance of the optical fiber link.

[0022] Optionally, the first optical signal also carries a data signal, with the detection sequence and data signal carried in different fields, or the detection sequence modulated over the data signal (with the detection sequence and data signal carried in the same field). For example, the first optical signal includes multiple sub-optical signals, each corresponding one-to-one with multiple sub-detection sequences. Each sub-optical signal carries a corresponding sub-detection sequence, and at least one of the multiple sub-optical signals carries a data signal. In each of these at least one sub-optical signals: the sub-detection sequence and data signal are carried in different fields (e.g., the sub-optical signal carries the sub-detection sequence and data signal in a time-division multiplexing manner, or the sub-optical signal carries the sub-detection sequence and data signal in a time-division multiplexed manner), or the sub-detection sequence is modulated over the data signal (with the sub-detection sequence and data signal carried in the same field).

[0023] Optionally, the first optical signal also carries a data signal, with the detection sequence modulated on top of the data signal. The modulation depth of the detection sequence is less than the modulation depth of the data signal, and the baud rate of the detection sequence is less than the baud rate of the data signal. For example, the first optical signal includes multiple sub-optical signals, at least one of which carries a sub-detection sequence and a data signal. In each of these at least one sub-optical signals: the sub-detection sequence is modulated on top of the data signal, the modulation depth of the sub-detection sequence is less than the modulation depth of the data signal, and the baud rate of the sub-detection sequence is less than the baud rate of the data signal.

[0024] The technical solution provided in this application addresses the issue that the detection sequence is considered noise for the data signal. Therefore, when the detection sequence is modulated onto the data signal, setting the modulation depth of the detection sequence to be less than the modulation depth of the data signal and setting the baud rate of the detection sequence to be less than the baud rate of the data signal can achieve the transmission performance of the fiber optic link with in-path detection while avoiding the detection sequence from affecting the data signal.

[0025] Optionally, the first optical signal also carries a data signal, and the detection sequence is modulated on the data signal. The ratio of the modulation depth of the detection sequence to the modulation depth of the data signal is less than a preset ratio, and the difference between the baud rate of the detection sequence and the baud rate of the data signal is within a preset range. For example, the first optical signal includes multiple sub-optical signals, at least one of which carries a sub-detection sequence and a data signal. In each of the at least one sub-optical signals: the sub-detection sequence is modulated on the data signal, the ratio of the modulation depth of the sub-detection sequence to the modulation depth of the data signal is less than a preset ratio, and the difference between the baud rate of the sub-detection sequence and the baud rate of the data signal is within a preset range.

[0026] The technical solution provided in this application, when the detection sequence is modulated over the data signal, has a smaller ratio of modulation depth of the detection sequence to modulation depth of the data signal than a preset ratio. This smaller ratio prevents the detection sequence from affecting the data signal. Furthermore, since the difference between the baud rate of the detection sequence and the baud rate of the data signal is within a preset range, the baud rate of the detection sequence is smaller than the baud rate of the data signal, but not excessively small. This avoids both the detection sequence affecting the data signal and the baud rate of the detection sequence being too small to make it difficult to detect the transmission performance of the fiber optic link.

[0027] Optionally, the autocorrelation curve corresponding to the detection sequence satisfies a preset condition. This autocorrelation curve is determined based on the autocorrelation curves of the multiple sub-detection sequences included in the detection sequence. For example, the autocorrelation value at each point on the autocorrelation curve corresponding to the detection sequence is equal to the sum of the autocorrelation values ​​at that point on the autocorrelation curves of the multiple sub-detection sequences. That is, the autocorrelation curve corresponding to the detection sequence is a superposition curve of the autocorrelation curves of the multiple sub-detection sequences.

[0028] The technical solution provided in this application allows the autocorrelation curve corresponding to the detection sequence to meet preset conditions, which facilitates the optical receiving device to determine the transmission performance of the optical fiber link based on the preset conditions and the autocorrelation curve corresponding to the detection sequence demodulated from the second optical signal.

[0029] Optionally, the autocorrelation curve corresponding to the detection sequence satisfies preset conditions, including: the autocorrelation curve corresponding to the detection sequence has a characteristic peak. For example, the autocorrelation curve corresponding to the detection sequence has only one characteristic peak.

[0030] The technical solution provided in this application provides that the autocorrelation curve corresponding to the detection sequence carried by the first optical signal has a characteristic peak, which facilitates the optical receiving device in determining the transmission performance of the optical fiber link based on the characteristic peak of the autocorrelation curve corresponding to the detection sequence demodulated from the second optical signal. Furthermore, since the autocorrelation curve corresponding to the detection sequence is a superposition curve of the autocorrelation curves of multiple sub-detection sequences included in the detection sequence, the peak value of the main peak of the autocorrelation curve corresponding to the detection sequence is relatively large, which helps to improve the sensitivity of detecting the transmission performance of the optical fiber link.

[0031] Optionally, the detection sequence may include any of the following: a pseudo-random code sequence; a Gray complement sequence.

[0032] Optionally, generating the first optical signal includes: modulating the driving signal of the light source using a detection sequence to generate the first optical signal. That is, modulating the detection sequence into the first optical signal using a direct modulation method. The direct modulation method is also called the internal modulation method. For example, the multiple sub-detection sequences included in the detection sequence are carried in the first optical signal in a wavelength division multiplexing manner. The first optical signal includes multiple sub-optical signals, which correspond one-to-one with the multiple sub-detection sequences. Each sub-optical signal is used to carry the corresponding sub-detection sequence. The multiple sub-detection sequences are used to modulate the driving signals of multiple light sources one-to-one, so that the multiple light sources emit the multiple sub-optical signals carrying the multiple sub-detection sequences one-to-one (that is, each light source emits a sub-optical signal carrying the corresponding sub-detection sequence). Then, the multiple sub-optical signals are multiplexed to obtain the first optical signal. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a first optical signal using parallel-fiber multiplexing. The first optical signal includes multiple sub-optical signals, each corresponding one-to-one with the multiple sub-detection sequences, with each sub-optical signal carrying its corresponding sub-detection sequence. The multiple sub-detection sequences are used to modulate the driving signals of multiple light sources one-to-one, so that each light source emits its corresponding sub-optical signal carrying the multiple sub-detection sequences (i.e., each light source emits its corresponding sub-detection sequence). As another example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a first optical signal using time-division multiplexing. The first optical signal carries the first sub-detection sequence in a first time period and the first optical signal carries the second sub-detection sequence in a second time period. In the first time period, the first sub-detection sequence is used to modulate the driving signal of the light source so that the light source emits a first optical signal carrying the first sub-detection sequence; in the second time period, the second sub-detection sequence is used to modulate the driving signal of the light source so that the light source emits a first optical signal carrying the second sub-detection sequence.

[0033] Optionally, generating the first optical signal includes: modulating the optical signal emitted by the light source using a detection sequence to generate the first optical signal. That is, using an external modulation method to modulate the detection sequence into the first optical signal. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in the first optical signal in a wavelength division multiplexing manner. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with the multiple sub-detection sequences, and each sub-optical signal is used to carry the corresponding sub-detection sequence. First, the multiple sub-detection sequences are used to modulate the sub-optical signals emitted by the multiple light sources one-to-one to obtain the multiple sub-optical signals carrying the multiple sub-detection sequences one-to-one; then, the multiple sub-optical signals are multiplexed to obtain the first optical signal. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a first optical signal using parallel-fiber multiplexing. The first optical signal includes multiple sub-optical signals, each corresponding one-to-one with the multiple sub-detection sequences, with each sub-optical signal carrying its corresponding sub-detection sequence. The multiple sub-detection sequences are used to modulate the sub-optical signals emitted by multiple light sources one-to-one, to obtain multiple sub-optical signals carrying the multiple sub-detection sequences. As another example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a first optical signal using time-division multiplexing. The first optical signal carries the first sub-detection sequence in a first time period and the first optical signal carries the second sub-detection sequence in a second time period. In the first time period, the first sub-detection sequence is used to modulate the optical signal emitted by the light source to obtain a first optical signal carrying the first sub-detection sequence; in the second time period, the second sub-detection sequence is used to modulate the optical signal emitted by the light source to obtain a first optical signal carrying the second sub-detection sequence.

[0034] Optionally, generating the first optical signal includes: modulating the driving signal of the light source with a data signal modulated with the detection sequence to generate the first optical signal. That is, the data signal and the detection sequence are modulated into the first optical signal using a direct modulation method. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in the first optical signal in a wavelength division multiplexing manner. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with the multiple sub-detection sequences and also corresponds one-to-one with multiple data signals. Each sub-optical signal is used to carry the corresponding data signal and the corresponding sub-detection sequence. First, the multiple sub-detection sequences are modulated one-to-one onto the multiple data signals. Then, the multiple data signals modulated with the multiple sub-detection sequences are used to modulate the driving signals of multiple light sources one-to-one, so that the multiple light sources emit the multiple sub-optical signals carrying the multiple sub-detection sequences and the multiple data signals one-to-one. Finally, the multiple sub-optical signals are multiplexed to obtain the first optical signal. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a first optical signal in a parallel-fiber multiplexing manner. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with the multiple sub-detection sequences and one-to-one with multiple data signals. Each sub-optical signal is used to carry the corresponding data signal and the corresponding sub-detection sequence. First, the multiple sub-detection sequences are modulated one-to-one onto the multiple data signals. Then, the multiple data signals modulated with the multiple sub-detection sequences are used to modulate the driving signals of multiple light sources one-to-one, so that the multiple light sources emit the multiple sub-optical signals carrying the multiple sub-detection sequences and the multiple data signals one-to-one. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a time-division multiplexed manner in a first optical signal. The first optical signal carries the first sub-detection sequence and a first data signal in a first time period, and carries a second sub-detection sequence and a second data signal in a second time period. In the first time period, the driving signal of the light source is modulated with the first data signal modulated with the first sub-detection sequence, causing the light source to emit a first optical signal carrying the first sub-detection sequence and the first data signal. In the second time period, the driving signal of the light source is modulated with the second data signal modulated with the second sub-detection sequence, causing the light source to emit a first optical signal carrying the second sub-detection sequence and the second data signal. In this case, the detection sequence is modulated onto the data signal. For example, in each sub-optical signal, the sub-detection sequence is modulated onto the data signal.

[0035] Optionally, generating the first optical signal includes: sequentially modulating the driving signal of the light source using a data signal and a detection sequence to generate the first optical signal. That is, the data signal and the detection sequence are modulated into the first optical signal using a direct modulation method. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in the first optical signal in a wavelength division multiplexing manner. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with the multiple sub-detection sequences and one-to-one with multiple data signals. Each sub-optical signal is used to carry the corresponding data signal and the corresponding sub-detection sequence. First, the multiple data signals are modulated one-to-one with the driving signals of the multiple light sources. Then, the multiple sub-detection sequences are modulated one-to-one with the driving signals of the multiple light sources that are modulated with the multiple data signals, so that the multiple light sources emit the multiple sub-optical signals carrying the multiple sub-detection sequences and the multiple data signals in a one-to-one correspondence. Finally, the multiple sub-optical signals are multiplexed to obtain the first optical signal. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a first optical signal in a parallel-fiber multiplexing manner. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with the multiple sub-detection sequences and one-to-one with multiple data signals. Each sub-optical signal is used to carry the corresponding data signal and the corresponding sub-detection sequence. First, the multiple data signals are used to modulate the driving signals of the multiple light sources one-to-one. Then, the multiple sub-detection sequences are used to modulate the driving signals of the multiple light sources that are modulated with the multiple data signals, so that the multiple light sources emit the multiple sub-optical signals carrying the multiple sub-detection sequences and the multiple data signals one-to-one. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a time-division multiplexed manner in a first optical signal. The first optical signal carries the first sub-detection sequence and a first data signal in a first time period, and carries a second sub-detection sequence and a second data signal in a second time period. In the first time period, the first data signal and the first sub-detection sequence are used to sequentially modulate the driving signal of the light source, causing the light source to emit a first optical signal carrying the first sub-detection sequence and the first data signal. In the second time period, the second data signal and the second sub-detection sequence are used to sequentially modulate the driving signal of the light source, causing the light source to emit a first optical signal carrying the second sub-detection sequence and the second data signal. In this case, the detection sequence is modulated on top of the data signal. For example, in each sub-optical signal, the sub-detection sequence is modulated on top of the data signal.

[0036] Optionally, generating the first optical signal includes: modulating an optical signal emitted by a light source with a data signal modulated with a detection sequence to generate the first optical signal. That is, using an external modulation method to modulate the data signal and the detection sequence into the first optical signal. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in the first optical signal in a wavelength division multiplexing manner. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with the multiple sub-detection sequences and also corresponds one-to-one with multiple data signals. Each sub-optical signal is used to carry the corresponding data signal and the corresponding sub-detection sequence. First, the multiple sub-detection sequences are modulated one-to-one onto the multiple data signals. Then, the multiple data signals modulated with the multiple sub-detection sequences are used to modulate the sub-optical signals emitted by the multiple light sources one-to-one to obtain multiple sub-optical signals carrying the multiple sub-detection sequences and the multiple data signals. Finally, the multiple sub-optical signals are multiplexed to obtain the first optical signal. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a first optical signal in a parallel-fiber multiplexing manner. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with the multiple sub-detection sequences and also corresponds one-to-one with multiple data signals. Each sub-optical signal is used to carry the corresponding data signal and the corresponding sub-detection sequence. First, the multiple sub-detection sequences are modulated one-to-one onto the multiple data signals. Then, the multiple data signals modulated with the multiple sub-detection sequences are used to modulate the sub-optical signals emitted by multiple light sources one-to-one, so as to obtain the multiple sub-optical signals that carry the multiple sub-detection sequences and the multiple data signals one-to-one. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a time-division multiplexed manner in a first optical signal. The first optical signal carries the first sub-detection sequence and a first data signal in a first time period, and carries a second sub-detection sequence and a second data signal in a second time period. In the first time period, the first data signal modulated with the first sub-detection sequence is used to modulate the optical signal emitted by the light source to obtain a first optical signal carrying the first sub-detection sequence and the first data signal. In the second time period, the second data signal modulated with the second sub-detection sequence is used to modulate the optical signal emitted by the light source to obtain a first optical signal carrying the second sub-detection sequence and the second data signal. In this case, the detection sequence is modulated onto the data signal. For example, in each sub-optical signal, the sub-detection sequence is modulated onto the data signal.

[0037] Optionally, generating the first optical signal includes: sequentially modulating the optical signal emitted by the light source using a data signal and a detection sequence to generate the first optical signal. That is, using an external modulation method to modulate the data signal and the detection sequence into the first optical signal. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in the first optical signal in a wavelength division multiplexing manner. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with the multiple sub-detection sequences and also corresponds one-to-one with multiple data signals. Each sub-optical signal is used to carry the corresponding data signal and the corresponding sub-detection sequence. First, the multiple data signals are modulated one-to-one with the multiple optical signals emitted by multiple light sources. Then, the multiple sub-detection sequences are used to modulate the multiple optical signals carrying the multiple data signals to obtain multiple sub-optical signals carrying the multiple sub-detection sequences and the multiple data signals. Finally, the multiple sub-optical signals are multiplexed to obtain the first optical signal. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a first optical signal in a parallel-fiber multiplexing manner. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with the multiple sub-detection sequences and one-to-one with multiple data signals. Each sub-optical signal is used to carry the corresponding data signal and the corresponding sub-detection sequence. First, the multiple data signals are used to modulate the multiple optical signals emitted by multiple light sources one-to-one. Then, the multiple sub-detection sequences are used to modulate the multiple optical signals carrying the multiple data signals one-to-one, so as to obtain the multiple sub-optical signals carrying the multiple sub-detection sequences and the multiple data signals one-to-one. For example, the detection sequence includes multiple sub-detection sequences carried in a time-division multiplexed manner within a first optical signal. The first optical signal carries the first sub-detection sequence and a first data signal in a first time period, and carries a second sub-detection sequence and a second data signal in a second time period. In the first time period, the first data signal and the first sub-detection sequence are used to sequentially modulate the optical signal emitted by the light source to obtain a first optical signal carrying the first sub-detection sequence and the first data signal. In the second time period, the second data signal and the second sub-detection sequence are used to sequentially modulate the optical signal emitted by the light source to obtain a first optical signal carrying the second sub-detection sequence and the second data signal. In this case, the detection sequence is modulated onto the data signal. For example, in each sub-optical signal, the sub-detection sequence is modulated onto the data signal.

[0038] Optionally, generating the first optical signal includes: modulating the driving signal of the light source with a data signal and modulating the optical signal emitted by the light source with a detection sequence to generate the first optical signal. That is, the data signal is modulated into the first optical signal using direct modulation, and the detection sequence is modulated into the first optical signal using external modulation. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in the first optical signal in a wavelength division multiplexing manner. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with the multiple sub-detection sequences and one-to-one with multiple data signals. Each sub-optical signal is used to carry the corresponding data signal and the corresponding sub-detection sequence. First, the multiple data signals are modulated one-to-one with the driving signals of the multiple light sources so that the multiple light sources emit multiple optical signals carrying the multiple data signals one-to-one. Then, the multiple sub-detection sequences are modulated one-to-one with the multiple optical signals to obtain multiple sub-optical signals carrying the multiple sub-detection sequences and the multiple data signals one-to-one. Finally, the multiple sub-optical signals are multiplexed to obtain the first optical signal. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a first optical signal in a parallel-fiber multiplexing manner. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with the multiple sub-detection sequences and one-to-one with multiple data signals. Each sub-optical signal is used to carry the corresponding data signal and the corresponding sub-detection sequence. First, the multiple data signals are modulated one-to-one with the driving signals of the multiple light sources so that the multiple light sources emit multiple optical signals carrying the multiple data signals one-to-one. Then, the multiple sub-detection sequences are modulated one-to-one with the multiple optical signals to obtain multiple sub-optical signals carrying the multiple sub-detection sequences and the multiple data signals one-to-one. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a time-division multiplexed manner within a first optical signal. The first optical signal carries the first sub-detection sequence and a first data signal in a first time period, and carries a second sub-detection sequence and a second data signal in a second time period. In the first time period: firstly, the driving signal of the light source is modulated using the first data signal to cause the light source to emit an optical signal carrying the first data signal; then, the first sub-detection sequence is used to modulate this optical signal to obtain a first optical signal carrying the first sub-detection sequence and the first data signal. In the second time period: firstly, the driving signal of the light source is modulated using the second data signal to cause the light source to emit an optical signal carrying the second data signal; then, the second sub-detection sequence is used to modulate this optical signal to obtain a first optical signal carrying the second sub-detection sequence and the second data signal. In this case, the detection sequence is modulated over the data signal. For example, in each sub-optical signal, the sub-detection sequence is modulated over the data signal.

[0039] Optionally, generating the first optical signal includes: modulating the driving signal of the light source using a detection sequence, and modulating the optical signal emitted by the light source using a data signal to generate the first optical signal. That is, the detection sequence is modulated into the first optical signal using direct modulation, and the data signal is modulated into the first optical signal using external modulation. For example, the multiple sub-detection sequences included in the detection sequence are carried in the first optical signal in a wavelength division multiplexing manner. The first optical signal includes multiple sub-optical signals, which correspond one-to-one with the multiple sub-detection sequences and one-to-one with multiple data signals. Each sub-optical signal is used to carry the corresponding data signal and the corresponding sub-detection sequence. First, the multiple sub-detection sequences are modulated one-to-one with the driving signals of multiple light sources so that the multiple light sources emit multiple optical signals carrying the multiple sub-detection sequences one-to-one. Then, the multiple data signals are modulated one-to-one with the multiple optical signals to obtain multiple sub-optical signals carrying the multiple sub-detection sequences and the multiple data signals one-to-one. Finally, the multiple sub-optical signals are multiplexed to obtain the first optical signal. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a first optical signal in a parallel-fiber multiplexing manner. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with the multiple sub-detection sequences and one-to-one with multiple data signals. Each sub-optical signal is used to carry the corresponding data signal and the corresponding sub-detection sequence. First, the multiple sub-detection sequences are used to modulate the driving signals of multiple light sources one-to-one, so that the multiple light sources emit multiple optical signals carrying the multiple sub-detection sequences one-to-one. Then, the multiple data signals are used to modulate the multiple optical signals one-to-one, so as to obtain multiple sub-optical signals carrying the multiple sub-detection sequences and the multiple data signals one-to-one. For example, the detection sequence includes the aforementioned multiple sub-detection sequences carried in a time-division multiplexed manner in a first optical signal. The first optical signal carries the first sub-detection sequence and a first data signal in a first time period, and carries a second sub-detection sequence and a second data signal in a second time period. In the first time period: firstly, the driving signal of the light source is modulated using the first sub-detection sequence to make the light source emit an optical signal carrying the first sub-detection sequence; then, the optical signal is modulated using the first data signal to obtain a first optical signal carrying the first sub-detection sequence and the first data signal. In the second time period: firstly, the driving signal of the light source is modulated using the second sub-detection sequence to make the light source emit an optical signal carrying the second sub-detection sequence; then, the optical signal is modulated using the second data signal to obtain a first optical signal carrying the second sub-detection sequence and the second data signal. In this case, the detection sequence is modulated on top of the data signal. For example, in each sub-optical signal, the sub-detection sequence is modulated on top of the data signal.

[0040] Optionally, in the first optical signal, the baud rates of the plurality of sub-detection sequences are equal. For example, the first optical signal includes a plurality of sub-optical signals, each of which carries a plurality of sub-detection sequences in a one-to-one correspondence, and the baud rates of the plurality of sub-detection sequences carried by the plurality of sub-optical signals are equal.

[0041] Optionally, the detection method is performed by an optical transmitting device, an optical module in the optical transmitting device, or an optical fiber card in the optical transmitting device.

[0042] Secondly, a method for detecting an optical fiber link is provided, applied to an optical receiving device. The method includes: receiving a second optical signal through the optical fiber link, the second optical signal including a first optical signal and a reflected optical signal. The first optical signal is an optical signal generated by an optical transmitting device and carries a detection sequence, which includes multiple sub-detection sequences carried in a multiplexed manner within the first optical signal; demodulating the second optical signal to obtain the detection sequence; and determining the transmission performance of the optical fiber link based on the demodulated detection sequence. The reflected optical signal is an optical signal generated by the reflection of the first optical signal within the optical fiber link. For example, the reflected optical signal is an optical signal generated by multiple (e.g., an even number of) reflections of the first optical signal between reflection points on the optical fiber link, including connectors, the end face of a laser in the optical transmitting device, etc. The intensity of the reflected optical signal depends on the reflection intensity of the reflection points.

[0043] The technical solution provided in this application involves an optical transmitting device transmitting a first optical signal carrying a detection sequence through an optical fiber link between the transmitting device and an optical receiving device. The first optical signal is then transmitted through the optical fiber link and converted into a second optical signal. After receiving the second optical signal, the optical receiving device determines the transmission performance of the optical fiber link based on the detection sequence carried by the second optical signal. Therefore, this application utilizes existing optical transmitting and receiving devices in an optical fiber communication system to detect the transmission performance of an optical fiber link. It eliminates the need for additional equipment such as an OTDR in the optical fiber link to perform the detection, resulting in simple hardware implementation and low detection costs.

[0044] Optionally, the multiplexing method includes any of the following: wavelength division multiplexing, parallel fiber multiplexing, or time division multiplexing.

[0045] Optionally, the multiplexing method is wavelength division multiplexing (WDM). The first optical signal includes multiple sub-optical signals, each corresponding one-to-one with a multiple sub-detection sequence. Any two sub-optical signals have different wavelengths (i.e., the wavelengths of the multiple sub-optical signals are all different). The optical fiber link includes a first optical fiber used to transmit the multiple sub-optical signals. For example, the first optical signal is obtained by multiplexing the multiple sub-optical signals using an optical transmitting device, and the first optical fiber is used to transmit the first optical signal for transmitting the multiple sub-optical signals.

[0046] The technical solution provided in this application, in the wavelength division multiplexing (WDM) method, uses a first optical fiber to transmit multiple sub-optical signals including the first optical signal. Therefore, the WDM method helps to save optical fiber resources, and the benefits of applying the WDM method in long-distance optical fiber communication systems are significant.

[0047] Optionally, the multiplexing method is a parallel fiber multiplexing method; the first optical signal includes multiple sub-optical signals, each corresponding one-to-one with a multiple sub-detection sequence; the optical fiber link includes a first optical fiber and a second optical fiber in parallel, the first optical fiber being used to transmit the first sub-optical signal, and the second optical fiber being used to transmit the second sub-optical signal, the multiple sub-optical signals including the first sub-optical signal and the second sub-optical signal. For example, the optical fiber link includes multiple parallel optical fibers, each corresponding one-to-one with a multiple sub-optical signal, each fiber being used to transmit its corresponding sub-optical signal.

[0048] The technical solution provided in this application uses multiple parallel optical fibers to transmit multiple sub-optical signals included in the first optical signal in a one-to-one correspondence in the parallel fiber multiplexing method. Therefore, the parallel fiber multiplexing method requires relatively more optical fiber resources and is usually used in short-distance optical fiber communication systems.

[0049] Optionally, the first optical fiber and the second optical fiber satisfy the following conditions: the lengths of the first optical fiber and the second optical fiber are the same; and the positions of the connectors on the first optical fiber and the second optical fiber are the same. For example, the first optical fiber and the second optical fiber are encapsulated in the same optical cable, and the connectors on the first optical fiber and the second optical fiber are MPO connectors on the optical cable.

[0050] The technical solution provided in this application, because the lengths of the first and second optical fibers are the same, and the positions of the connectors on the first and second optical fibers are also the same, means that the influence of the first optical fiber on the first sub-optical signal is the same as the influence of the second optical fiber on the second sub-optical signal. This facilitates the joint detection of the transmission performance of the optical fiber link using the sub-detection sequences carried by the first and second sub-optical signals. For example, if the first and second optical fibers are encapsulated in the same optical cable, the same MPO connector on this cable has the same influence on both fibers, thus having the same influence on the first sub-optical signal transmitted in the first fiber and the second sub-optical signal transmitted in the second fiber. The first and second sub-optical signals experience the same physical environment during transmission. Furthermore, encapsulating the first and second optical fibers in the same optical cable improves the integration of the optical fiber link and facilitates its deployment and connection.

[0051] Optionally, the plurality of sub-detection sequences include a first sub-detection sequence, and the plurality of sub-optical signals include a first sub-optical signal. The first sub-optical signal corresponds to the first sub-detection sequence, and the first sub-optical signal carries a plurality of first sub-detection sequences, which are periodically distributed in the first sub-optical signal. There are boundary markers between adjacent first sub-detection sequences among the plurality of first sub-detection sequences; or, adjacent first sub-detection sequences among the plurality of first sub-detection sequences are consecutive. The first sub-detection sequence can be any one of the plurality of sub-detection sequences, and the first sub-optical signal is used to carry the first sub-detection sequence. After transmission via the optical fiber link, the first sub-optical signal becomes a third sub-optical signal, which includes the first sub-optical signal and a first sub-reflected optical signal. The second optical signal includes the third sub-optical signal, and the reflected optical signal includes the first sub-reflected optical signal. The first sub-reflected optical signal is the optical signal generated by the reflection of the first sub-optical signal in the optical fiber link.

[0052] The technical solution provided in this application involves a first sub-optical signal carrying multiple periodically distributed first sub-detection sequences (correspondingly, a third sub-optical signal also carries multiple periodically distributed first sub-detection sequences). This facilitates the demodulation of the first sub-detection sequences from the third sub-optical signal by the optical receiving device, thereby enabling the determination of the fiber optic link's transmission performance based on the demodulated first sub-detection sequences from the third sub-optical signal. Furthermore, it reduces the difficulty for the optical receiving device to demodulate the first sub-detection sequences from the third sub-optical signal.

[0053] Optionally, the first sub-optical signal carries multiple first detection sub-sequences, and there is a boundary marker between adjacent first sub-detection sequences among the multiple first sub-detection sequences; after being transmitted via the optical fiber link, the first sub-optical signal becomes a third sub-optical signal, the third sub-optical signal includes the first sub-optical signal and a first sub-reflected optical signal, the second optical signal includes the third sub-optical signal, and the reflected optical signal includes the first sub-reflected optical signal, the first sub-reflected optical signal being the optical signal generated by the reflection of the first sub-optical signal in the optical fiber link; demodulating the second optical signal to obtain the detection sequence includes: determining the first sub-detection sequence carried by the third sub-optical signal according to the boundary marker carried by the third sub-optical signal.

[0054] The technical solution provided in this application has a boundary marker between adjacent first sub-detection sequences carried by the first sub-optical signal. Therefore, there is a boundary marker between adjacent first sub-detection sequences carried by the third sub-optical signal. The optical receiving device can identify the first sub-detection sequence carried by the third sub-optical signal based on the boundary marker carried by the third sub-optical signal, which reduces the difficulty for the optical receiving device to identify the first sub-detection sequence from the third sub-optical signal.

[0055] Optionally, the first sub-optical signal carries multiple first detection sub-sequences, and adjacent first sub-detection sequences in the multiple first sub-detection sequences are consecutive; the first sub-optical signal is transformed into a third sub-optical signal after being transmitted through the optical fiber link, the third sub-optical signal includes the first sub-optical signal and a first sub-reflected optical signal, the second optical signal includes the third sub-optical signal, the reflected optical signal includes the first sub-reflected optical signal, the first sub-reflected optical signal is the optical signal generated by the reflection of the first sub-optical signal in the optical fiber link; demodulating the second optical signal to obtain the detection sequence includes: determining the first sub-detection sequence carried by the third sub-optical signal based on the characteristics of the first sub-detection sequence.

[0056] The technical solution provided in this application allows the optical receiving device to determine the first sub-detection sequence carried by the third sub-optical signal based on the characteristics of the first sub-detection sequence, thereby facilitating the optical receiving device to determine the transmission performance of the optical fiber link based on the first sub-detection sequence carried by the third sub-optical signal.

[0057] Optionally, the multiplexing method is time-division multiplexing; the first optical signal carries a first sub-detection sequence in a first time period, and the first optical signal carries a second sub-detection sequence in a second time period. The plurality of sub-detection sequences includes the first sub-detection sequence and the second sub-detection sequence. The first sub-detection sequence and the second sub-detection sequence can be any two of the plurality of sub-detection sequences. For example, the plurality of sub-detection sequences correspond one-to-one with multiple time periods, and the first optical signal carries the corresponding sub-detection sequence in each of the plurality of time periods.

[0058] Optionally, the first optical signal carries multiple first sub-detection sequences in the first time period, and the multiple first sub-detection sequences are periodically distributed in the first optical signal; there are boundary markers between adjacent first sub-detection sequences among the multiple first sub-detection sequences; or, adjacent first sub-detection sequences among the multiple first sub-detection sequences are continuous.

[0059] The technical solution provided in this application involves a first optical signal carrying multiple periodically distributed first sub-detection sequences in a first time period (correspondingly, a second optical signal also carries multiple periodically distributed first sub-detection sequences), which facilitates the optical receiving device to demodulate the first sub-detection sequences from the second optical signal, and then determines the transmission performance of the optical fiber link based on the first sub-detection sequences demodulated from the second optical signal.

[0060] Optionally, the first optical signal carries multiple first sub-detection sequences in a first time period, and there is a boundary marker between adjacent first sub-detection sequences in the multiple first sub-detection sequences; demodulating the second optical signal to obtain a detection sequence includes: determining the first sub-detection sequence carried by the second optical signal based on the boundary marker carried by the second optical signal.

[0061] The technical solution provided in this application has a boundary marker between adjacent first sub-detection sequences carried by the first optical signal. Therefore, there is a boundary marker between adjacent first sub-detection sequences carried by the second optical signal. The optical receiving device can identify the first sub-detection sequence carried by the second optical signal based on the boundary marker carried by the second optical signal, which reduces the difficulty for the optical receiving device to identify the first sub-detection sequence from the second optical signal.

[0062] Optionally, the first optical signal carries multiple first sub-detection sequences in a first time period, and adjacent first sub-detection sequences in the multiple first sub-detection sequences are consecutive; demodulating the second optical signal to obtain a detection sequence includes: determining the first sub-detection sequence carried by the second optical signal based on the characteristics of the first sub-detection sequences.

[0063] The technical solution provided in this application allows the optical receiving device to determine the first sub-detection sequence carried by the second optical signal based on the characteristics of the first sub-detection sequence, thereby facilitating the optical receiving device to determine the transmission performance of the optical fiber link based on the first sub-detection sequence carried by the second optical signal.

[0064] Optionally, demodulating the second optical signal to obtain a detection sequence includes: demodulating the second optical signal to obtain the plurality of sub-detection sequences; correspondingly, determining the transmission performance of the optical fiber link based on the demodulated detection sequences includes: acquiring the correlation curve of each demodulated sub-detection sequence, where the correlation curve is an autocorrelation curve or a cross-correlation curve, and the cross-correlation curve of each demodulated sub-detection sequence is determined based on each demodulated sub-detection sequence and each known sub-detection sequence; determining the correlation curve corresponding to the demodulated detection sequence based on the correlation curves of the plurality of demodulated sub-detection sequences; and determining the transmission performance of the optical fiber link based on the correlation curve corresponding to the demodulated detection sequence. Wherein, the correlation value at each point on the correlation curve corresponding to the demodulated detection sequence is equal to the sum of the correlation values ​​at that point on the correlation curves of the plurality of demodulated sub-detection sequences. That is, the correlation curve corresponding to the demodulated detection sequence is a superposition curve of the correlation curves of the plurality of demodulated sub-detection sequences. Since the cross-correlation curve of each demodulated sub-detection sequence is determined based on the demodulated sub-detection sequence and the known sub-detection sequence, the cross-correlation curve of each demodulated sub-detection sequence can also be considered as the autocorrelation curve of that sub-detection sequence, and the correlation curve corresponding to the demodulated detection sequence can also be considered as the autocorrelation curve corresponding to that detection sequence. That is, the correlation curves described in this application can all be understood as autocorrelation curves.

[0065] The technical solution provided in this application allows an optical receiving device to determine the correlation curve corresponding to the demodulated detection sequence from the second optical signal based on the correlation curves of the plurality of sub-detection sequences demodulated from the second optical signal. The correlation curve corresponding to the demodulated detection sequence is a superposition curve of the correlation curves of the plurality of demodulated sub-detection sequences. The optical receiving device determines the transmission performance of the optical fiber link based on the correlation curve corresponding to the demodulated detection sequence from the second optical signal, which can improve the sensitivity of detecting the transmission performance of the optical fiber link.

[0066] Optionally, if the autocorrelation curve corresponding to the detection sequence meets a preset condition, the transmission performance of the optical fiber link is determined based on the correlation curve corresponding to the demodulated detection sequence, including: determining the transmission performance of the optical fiber link based on the correlation curve corresponding to the demodulated detection sequence and the preset condition.

[0067] Optionally, the autocorrelation curve corresponding to the detection sequence satisfies a preset condition, including: the autocorrelation curve corresponding to the detection sequence has a characteristic peak. For example, the autocorrelation curve corresponding to the detection sequence has only one characteristic peak. Determining the transmission performance of the optical fiber link based on the demodulated correlation curve corresponding to the detection sequence and the preset condition includes: determining the transmission performance of the optical fiber link based on the characteristic peak of the demodulated correlation curve corresponding to the detection sequence.

[0068] The technical solution provided in this application allows for the detection of fiber optic link transmission performance by means of a characteristic peak in the autocorrelation curve corresponding to the detection sequence carried by the first optical signal. Since the autocorrelation curve corresponding to the detection sequence demodulated from the second optical signal has a characteristic peak, the optical receiving device can determine the transmission performance of the fiber optic link based on this characteristic peak. Furthermore, because the autocorrelation curve corresponding to the detection sequence demodulated from the second optical signal is a superposition of the autocorrelation curves of the multiple sub-detection sequences demodulated from the second optical signal, the main peak of the autocorrelation curve corresponding to the detection sequence demodulated from the second optical signal has a relatively large peak value, which enhances the sensitivity of detecting the transmission performance of the fiber optic link.

[0069] Optionally, the transmission performance of the optical fiber link can be determined based on the characteristic peaks of the correlation curve corresponding to the demodulated detection sequence, including: determining that the optical fiber link is fault-free when the correlation curve corresponding to the demodulated detection sequence has only one characteristic peak; and determining that the optical fiber link is faulty when the correlation curve corresponding to the demodulated detection sequence has multiple characteristic peaks.

[0070] The technical solution provided in this application addresses the issue that, since the autocorrelation curve corresponding to the detection sequence carried by the first optical signal has only one characteristic peak, when the correlation curve (autocorrelation curve or cross-correlation curve) corresponding to the detection sequence demodulated from the second optical signal by the optical receiving device has multiple characteristic peaks, the secondary peaks among these characteristic peaks are caused by the optical signal (i.e., the reflected optical signal) generated by the reflection of the first optical signal in the optical fiber link. Since fault points in the optical fiber link typically reflect optical signals, when the correlation curve corresponding to the detection sequence demodulated from the second optical signal has multiple characteristic peaks, the optical receiving device determines that the optical fiber link is faulty; when the correlation curve corresponding to the detection sequence demodulated from the second optical signal has only one characteristic peak, the optical receiving device determines that the optical fiber link is fault-free.

[0071] Optionally, determining the transmission performance of the optical fiber link based on the characteristic peaks of the correlation curve corresponding to the demodulated detection sequence further includes: if the correlation curve corresponding to the demodulated detection sequence has multiple characteristic peaks, determining the fault point on the optical fiber link based on the primary peak and the secondary peak among the multiple characteristic peaks. The multiple characteristic peaks include one primary peak and at least one secondary peak, and the peak value of each of the at least one secondary peak is smaller than the peak value of the primary peak. The at least one secondary peak is caused by the optical signal generated by the reflection of the first optical signal in the optical fiber link (i.e., the reflected optical signal).

[0072] The technical solution provided in this application, when the correlation curve corresponding to the detection sequence demodulated from the second optical signal has multiple characteristic peaks, allows the optical receiving device to determine the fault point on the optical fiber link based on the main and secondary peaks among these characteristic peaks, thereby achieving fault location of the optical fiber link. Therefore, this application eliminates the need for personnel to carry instruments to the site for fault location, simplifying the process and reducing labor costs.

[0073] Optionally, the detection sequence may include any of the following: a pseudo-random code sequence; a Gray complement sequence.

[0074] Optionally, the first optical signal also carries a data signal. That is, the first optical signal carries a detection sequence and a data signal. For example, the first optical signal includes multiple sub-optical signals, which correspond one-to-one with multiple sub-detection sequences. Each sub-optical signal carries a corresponding sub-detection sequence, and at least one of the multiple sub-optical signals carries a data signal. The data signals carried by different sub-optical signals can be different.

[0075] The technical solution provided in this application carries a data signal and a detection sequence for detecting the transmission performance of the optical fiber link in the first optical signal, which can realize the in-path detection of the transmission performance of the optical fiber link.

[0076] Optionally, the first optical signal also carries a data signal, with the detection sequence and data signal carried in different fields, or the detection sequence modulated over the data signal (with the detection sequence and data signal carried in the same field). For example, the first optical signal includes multiple sub-optical signals, each corresponding one-to-one with multiple sub-detection sequences. Each sub-optical signal carries a corresponding sub-detection sequence, and at least one of the multiple sub-optical signals carries a data signal. In each of these at least one sub-optical signals: the sub-detection sequence and data signal are carried in different fields (e.g., the sub-optical signal carries the sub-detection sequence and data signal in a time-division multiplexing manner, or the sub-optical signal carries the sub-detection sequence and data signal in a time-division multiplexed manner), or the sub-detection sequence is modulated over the data signal (with the sub-detection sequence and data signal carried in the same field).

[0077] Optionally, the first optical signal also carries a data signal, with the detection sequence modulated on top of the data signal. The modulation depth of the detection sequence is less than the modulation depth of the data signal, and the baud rate of the detection sequence is less than the baud rate of the data signal. For example, the first optical signal includes multiple sub-optical signals, at least one of which carries a sub-detection sequence and a data signal. In each of these at least one sub-optical signals: the sub-detection sequence is modulated on top of the data signal, the modulation depth of the sub-detection sequence is less than the modulation depth of the data signal, and the baud rate of the sub-detection sequence is less than the baud rate of the data signal.

[0078] The technical solution provided in this application addresses the issue that the detection sequence is considered noise for the data signal. Therefore, when the detection sequence is modulated onto the data signal, setting the modulation depth of the detection sequence to be less than the modulation depth of the data signal and setting the baud rate of the detection sequence to be less than the baud rate of the data signal can achieve the transmission performance of the fiber optic link with in-path detection while avoiding the detection sequence from affecting the data signal.

[0079] Optionally, the first optical signal also carries a data signal, and the detection sequence is modulated on the data signal. The ratio of the modulation depth of the detection sequence to the modulation depth of the data signal is less than a preset ratio, and the difference between the baud rate of the detection sequence and the baud rate of the data signal is within a preset range. For example, the first optical signal includes multiple sub-optical signals, at least one of which carries a sub-detection sequence and a data signal. In each of the at least one sub-optical signals: the sub-detection sequence is modulated on the data signal, the ratio of the modulation depth of the sub-detection sequence to the modulation depth of the data signal is less than a preset ratio, and the difference between the baud rate of the sub-detection sequence and the baud rate of the data signal is within a preset range.

[0080] The technical solution provided in this application, when the detection sequence is modulated over the data signal, has a smaller ratio of modulation depth of the detection sequence to modulation depth of the data signal than a preset ratio. This smaller ratio prevents the detection sequence from affecting the data signal. Furthermore, since the difference between the baud rate of the detection sequence and the baud rate of the data signal is within a preset range, the baud rate of the detection sequence is smaller than the baud rate of the data signal, but not excessively small. This avoids both the detection sequence affecting the data signal and the baud rate of the detection sequence being too small to make it difficult to detect the transmission performance of the fiber optic link.

[0081] Optionally, in the first optical signal, the baud rates of the plurality of sub-detection sequences are equal. For example, the first optical signal includes a plurality of sub-optical signals, each of which carries a plurality of sub-detection sequences in a one-to-one correspondence, and the baud rates of the plurality of sub-detection sequences carried by the plurality of sub-optical signals are equal.

[0082] Thirdly, a fiber optic link detection device is provided, comprising at least one functional module for performing the method provided by the first aspect or any alternative method thereof. The at least one functional module may be implemented based on software, hardware, or a combination of both, and may be arbitrarily combined or divided based on a specific implementation.

[0083] Fourthly, a detection device for an optical fiber link is provided, comprising at least one functional module for performing the method provided by the second aspect or any alternative method thereof. The at least one functional module may be implemented based on software, hardware, or a combination of both, and may be arbitrarily combined or divided based on a specific implementation.

[0084] Fifthly, an apparatus for detecting an optical fiber link is provided, including a memory and a processor; the memory is used to store a computer program; the processor is used to execute the computer program stored in the memory to cause the detection apparatus to perform all or part of the steps of the method provided in the first aspect or any alternative method of the first aspect.

[0085] A sixth aspect provides an apparatus for detecting an optical fiber link, including a memory and a processor; the memory is used to store a computer program; the processor is used to execute the computer program stored in the memory to cause the detection apparatus to perform all or part of the steps of the method provided in the second aspect or any alternative method of the second aspect.

[0086] In a seventh aspect, a detection device for an optical fiber link is provided, comprising a main control board and an interface board, the main control board and the interface board being used to implement all or part of the steps of the method provided in the first aspect or any alternative method of the first aspect.

[0087] Eighthly, a detection device for an optical fiber link is provided, comprising a main control board and an interface board, the main control board and the interface board being used to implement all or part of the steps of the method provided in the second aspect or any alternative method of the second aspect described above.

[0088] Optionally, in the third, fifth, and seventh aspects described above, the detection device is an optical transmitting device, an optical module within the optical transmitting device, or a fiber optic card within the optical transmitting device; alternatively, the detection device is integrated into the optical transmitting device, an optical module within the optical transmitting device, or a fiber optic card within the optical transmitting device. In the fourth, sixth, and eighth aspects described above, the detection device is an optical receiving device, an optical module within the optical receiving device, or a fiber optic card within the optical receiving device; alternatively, the detection device is integrated into the optical receiving device, an optical module within the optical receiving device, or a fiber optic card within the optical receiving device.

[0089] A ninth aspect provides an optical fiber link detection apparatus, including a processor and an optical device; the optical device is used to perform transmit / receive operations as provided in the first aspect or any alternative method of the first aspect; the processor is used to perform operations other than transmit / receive operations in the method provided in the first aspect or any alternative method of the first aspect.

[0090] In a tenth aspect, an apparatus for detecting an optical fiber link is provided, comprising a processor and an optical device; the optical device is used to perform transmit / receive operations as provided in the method of the second aspect or any alternative method thereof; the processor is used to perform operations other than transmit / receive operations in the method of the second aspect or any alternative method thereof.

[0091] Optionally, in the ninth and tenth aspects above, the processor includes an optical digital signal processor (ODSP); the optical device includes at least one of an optical transmitter or an optical receiver.

[0092] Optionally, in the ninth and tenth aspects mentioned above, the detection device is an optical module or a light card.

[0093] Eleventhly, an optical fiber communication system is provided, including an optical transmitting device, an optical receiving device, and an optical fiber link, wherein the optical transmitting device and the optical receiving device are connected via the optical fiber link; the optical transmitting device includes an optical fiber link detection device as provided in the third, fifth, seventh, or ninth aspects above; and the optical receiving device includes an optical fiber link detection device as provided in the fourth, sixth, eighth, or tenth aspects above.

[0094] In a twelfth aspect, a computer-readable storage medium is provided, which stores a computer program that, when executed, implements at least some steps of the method provided by the first aspect or any alternative method of the first aspect, or implements at least some steps of the method provided by the second aspect or any alternative method of the second aspect.

[0095] In a thirteenth aspect, a computer program product is provided, comprising a program or code that, when executed, implements at least some steps of the method provided by the first aspect or any alternative method thereof, or implements at least some steps of the method provided by the second aspect or any alternative method thereof.

[0096] In a fourteenth aspect, a chip is provided, the chip including programmable logic circuitry and / or program instructions, the chip being configured to implement at least some steps of the method provided by the first aspect or any alternative method of the first aspect above, or to implement at least some steps of the method provided by the second aspect or any alternative method of the second aspect above.

[0097] The technical effects of the third to fourteenth aspects mentioned above can be referred to the technical effects of the first to second aspects, and will not be elaborated here. Attached Figure Description

[0098] Figure 1 This is a schematic diagram of an optical fiber communication system provided in an embodiment of this application;

[0099] Figure 2 This is a schematic diagram of another optical fiber communication system provided in an embodiment of this application;

[0100] Figure 3 This is a flowchart of a fiber optic link detection method provided in an embodiment of this application;

[0101] Figure 4 This is a schematic diagram of a sub-detection sequence X1 provided in an embodiment of this application;

[0102] Figure 5 This is a schematic diagram of a sub-detection sequence X2 provided in an embodiment of this application;

[0103] Figure 6 This is a schematic diagram of a sub-detection sequence X3 provided in an embodiment of this application;

[0104] Figure 7 This is a schematic diagram of a sub-detection sequence X4 provided in an embodiment of this application;

[0105] Figure 8 This is a schematic diagram of the autocorrelation curve of a sub-detection sequence X1 provided in an embodiment of this application;

[0106] Figure 9 This is a schematic diagram of the autocorrelation curve of a sub-detection sequence X2 provided in an embodiment of this application;

[0107] Figure 10 This is a schematic diagram of the autocorrelation curve of a sub-detection sequence X3 provided in an embodiment of this application;

[0108] Figure 11 This is a schematic diagram of the autocorrelation curve of a sub-detection sequence X4 provided in an embodiment of this application;

[0109] Figure 12 This is a schematic diagram of the autocorrelation curve corresponding to a detection sequence X provided in an embodiment of this application;

[0110] Figure 13 This is a schematic diagram of another optical fiber communication system provided in an embodiment of this application;

[0111] Figure 14 This is a schematic diagram of yet another optical fiber communication system provided in the embodiments of this application;

[0112] Figure 15 This is a schematic diagram showing the distribution of multiple first sub-detection sequences in a first sub-optical signal according to an embodiment of this application;

[0113] Figure 16 This is another schematic diagram showing the distribution of multiple first sub-detection sequences in the first sub-optical signal provided in the embodiments of this application;

[0114] Figure 17 This is a schematic diagram of generating a first sub-optical signal provided in an embodiment of this application;

[0115] Figure 18 This is a schematic diagram of another method for generating the first sub-optical signal provided in an embodiment of this application;

[0116] Figure 19 This is a schematic diagram of yet another optical fiber communication system provided in the embodiments of this application;

[0117] Figure 20 This is a schematic diagram of another method for generating a first sub-optical signal provided in an embodiment of this application;

[0118] Figure 21 This is a schematic diagram of another method for generating a first sub-optical signal provided in an embodiment of this application;

[0119] Figure 22 This is a schematic diagram of another method for generating a first sub-optical signal provided in an embodiment of this application;

[0120] Figure 23 This is a schematic diagram of another method for generating a first sub-optical signal provided in an embodiment of this application;

[0121] Figure 24 This is a schematic diagram of another method for generating a first sub-optical signal provided in an embodiment of this application;

[0122] Figure 25 This is a schematic diagram of another method for generating a first sub-optical signal provided in an embodiment of this application;

[0123] Figure 26 This is a schematic diagram of the correlation curve corresponding to the detection sequence X demodulated from the second optical signal, provided in an embodiment of this application;

[0124] Figure 27 This is a schematic diagram of a fiber optic link detection device provided in an embodiment of this application;

[0125] Figure 28 This is a schematic diagram of another fiber optic link detection device provided in an embodiment of this application;

[0126] Figure 29 This is a schematic diagram of another fiber optic link detection device provided in an embodiment of this application;

[0127] Figure 30 This is a schematic diagram of another fiber optic link detection device provided in the embodiments of this application. Detailed Implementation

[0128] The embodiments of this application will now be described in further detail with reference to the accompanying drawings.

[0129] An optical fiber communication system is a communication system that uses optical fiber as the transmission medium. By modulating information onto optical signals and transmitting them through optical fibers, an optical fiber communication system can achieve high-speed, long-distance, and high-capacity communication transmission.

[0130] Fiber optic communication systems typically consist of optical transmitting equipment, optical receiving equipment, and fiber optic links. The optical transmitting equipment and optical receiving equipment are connected via fiber optic links. The optical transmitting equipment modulates the information to be transmitted onto an optical signal and then transmits this optical signal to the optical receiving equipment via the fiber optic link. The optical receiving equipment receives the optical signal via the fiber optic link and demodulates the information carried by the optical signal. Abnormalities in the fiber optic link can cause multipath interference (MPI) noise, mode partition noise (MPN), etc., leading to a deterioration in the signal-to-noise ratio (SNR) of the optical signal received by the optical receiving equipment. Specifically, a fiber optic link typically consists of multiple fiber segments and multiple connectors. Connectors are used to connect the optical transmitting equipment, optical receiving equipment, and optical fibers. If the end face of the connector is dirty or the connector is loose, resulting in poor contact, the optical signal transmitted in the fiber optic link (for ease of distinction, this optical signal is referred to as the original optical signal) will experience significant reflection at the connector. Optical signals reflected back and forth between different connectors, and between connectors and the end face of the laser in the optical transmitting device (the laser end face of the optical transmitting device has strong reflectivity and can be considered a fixed reflection point), are superimposed on the original optical signal, generating MPI noise that is related to the original optical signal but has a delay. The delay of MPI noise depends on the length of the fiber between the two reflection points reflecting the MPI noise (e.g., two connectors, or one connector and the laser end face of the optical transmitting device). In multimode scenarios, reflections caused by connectors and the laser end face of the optical transmitting device can also induce MPN (Multiple-Noise Reduction). Both MPI noise and MPN degrade the signal-to-noise ratio (SNR) of the optical signal received by the optical receiving device, affecting the transmission performance of the optical fiber transmission system, and even causing optical fiber link interruptions (the situation where noise superimposed on the original optical signal causes the optical receiving device to be unable to correctly demodulate the service data from the received optical signal for a short period of time). The signal-to-noise ratio of the optical signal is also called the optical signal-to-noise ratio (OSNR). Optical transmitting equipment and optical receiving equipment are collectively referred to as optical communication equipment. The terms "optical transmitting equipment" and "optical receiving equipment" are relative; any optical communication equipment in an optical fiber communication system can function as either an optical transmitting equipment or an optical receiving equipment.

[0131] For example, please refer to Figure 1The diagram illustrates a schematic of an optical fiber communication system. This system includes station 110 and station 120, which are connected via optical fiber link 130 and optical fiber link 140. Both station 110 and station 120 are optical communication devices. Optical fiber link 130 is a unidirectional link for communication between station 110 and station 120, and includes multiple optical fiber segments 131 and multiple connectors 132. Figure 1 The diagram shows two connectors 132, with adjacent fiber optic segments 131 connected via connectors 132. Fiber optic link 140 is a unidirectional link for communication between station 120 and station 110, and includes multiple fiber optic segments 141 and multiple connectors 142. Figure 1The diagram shows two connectors 142, with adjacent fiber segments 141 connected via connectors 142. Station 110 modulates the information to be transmitted onto an optical signal and then transmits this optical signal (e.g., referred to as the original optical signal 1) to station 120 via fiber optic link 130. Station 120 receives the optical signal via fiber optic link 130 and demodulates the information carried by the optical signal. During the transmission of the original optical signal 1 through fiber optic link 130, if the end face of connector 132 on fiber optic link 130 is dirty or the connector 132 is loose, resulting in poor contact, the original optical signal 1 will experience significant reflection at connector 132. The optical signals reflected back and forth between different connectors 132, as well as the optical signals reflected back and forth between connector 132 and the end face of the laser at station 110, will be superimposed on the original optical signal 1, generating MPI noise related to the original optical signal 1 but with a delay. In multimode scenarios, multiple reflections caused by reflection points such as connector 132 and the end face of the laser can also trigger MPN. Both MPI noise and MPN (Multi-Purpose Noise) degrade the signal-to-noise ratio of the optical signal received at station 120, affecting the transmission performance of the optical fiber transmission system and even causing intermittent interruptions in the optical fiber link 130. Similarly, station 120 modulates the information to be transmitted onto an optical signal and then transmits this optical signal (e.g., referred to as the original optical signal 2) to station 110 via optical fiber link 140. Station 110 receives the optical signal via optical fiber link 140 and demodulates the information carried by the optical signal. During the transmission of the original optical signal 2 in optical fiber link 140, if the end face of the connector 142 on the optical fiber link 140 is dirty or the connector 142 is loose, resulting in poor contact, the original optical signal 2 will experience significant reflection at the connector 142. The optical signals reflected back and forth between different connectors 142, as well as the optical signals reflected back and forth between the connector 142 and the end face of the laser at station 120, will be superimposed on the original optical signal 2, generating MPI noise that is related to the original optical signal 2 but has a delay. In multimode scenarios, multiple reflections caused by reflection points such as connector 142 and the laser end face can also trigger MPN. Both MPI noise and MPN can degrade the signal-to-noise ratio of the optical signal received by site 110, affecting the transmission performance of the optical fiber transmission system, and even causing the optical fiber link 140 to momentarily disconnect.

[0132] As described above, the fiber optic link's impact on the transmission performance of a fiber optic transmission system is crucial. Therefore, to prevent fiber optic link anomalies from affecting the transmission performance of the fiber optic transmission system, it is necessary to monitor the fiber optic link's transmission performance. For example, the length of a typical fiber optic link is usually from a few meters to tens of kilometers. The fiber optic link's transmission performance can be monitored when the transmission performance of the fiber optic transmission system deteriorates, or even when the transmission performance of the fiber optic transmission system has not deteriorated, such as during the initial setup phase, or periodically to provide early warning of potential performance issues.

[0133] Currently, optical time domain reflectometers (OTDRs) are commonly used to detect the transmission performance of fiber optic links. OTDRs are based on time-domain reflectometry to detect the transmission performance of fiber optic links, such as loss, attenuation, reflection, and fault location. For example, an OTDR is deployed in a fiber optic link, controlling it to transmit an optical signal through the link and detect the reflected optical signal. The transmission performance of the fiber optic link is determined based on the reflected optical signal detected by the OTDR. For instance, the presence and location of faults in the fiber optic link can be determined based on the time, intensity, and waveform of the reflected optical signal detected by the OTDR. Specifically, an OTDR consists of a laser and a detector, deployed at the same end of the fiber optic link. The laser transmits an optical signal through the link, and the detector detects the reflected optical signal after the laser has transmitted the signal. In order for the reflected light signal to enter the detector, a circulator or power divider needs to be deployed on the fiber optic link, and the detector is connected to the fiber optic link through the circulator or power divider. The reflected light signal is coupled to the detector through the power divider or circulator so that the detector can detect the reflected light signal.

[0134] However, using OTDR to test the transmission performance of fiber optic links requires deploying hardware such as OTDRs and circulators (or power dividers) in the fiber optic link, and also requires fiber optic plugging and unplugging. This makes the hardware implementation for testing fiber optic links complex, the testing cost high, and the implementation process complicated.

[0135] In addition to using OTDR to test the transmission performance of fiber optic links, staff can also carry instruments to the site to locate faults in fiber optic links. However, this method is cumbersome to operate, complex to implement, and has high manpower costs.

[0136] This application provides a method and apparatus for detecting optical fiber links, as well as an optical fiber communication system. The optical fiber communication system includes an optical transmitting device, an optical receiving device, and an optical fiber link, with the optical transmitting device and the optical receiving device connected via the optical fiber link. The optical transmitting device sends an optical signal carrying a detection sequence to the optical receiving device via the optical fiber link. The optical receiving device receives the optical signal via the optical fiber link and determines the transmission performance of the optical fiber link based on the detection sequence carried by the received optical signal. This achieves the detection of the transmission performance of the optical fiber link. As can be seen, this application utilizes the existing optical transmitting and receiving devices of the optical fiber communication system to detect the transmission performance of the optical fiber link. It eliminates the need to deploy additional equipment such as OTDRs, circulators (or power dividers) in the optical fiber link, and eliminates the need for fiber optic plugging and unplugging. Therefore, the hardware implementation for detecting the transmission performance of the optical fiber link is simple, the detection cost is low, and it enables in-line detection. Furthermore, it eliminates the need for personnel to carry instruments to the site for fault location, resulting in low labor costs for detection.

[0137] The technical solutions of the embodiments of this application are described below. First, the application scenarios of the embodiments of this application are introduced.

[0138] Please refer to Figure 2 This diagram illustrates an application scenario provided by an embodiment of this application. The application scenario provides an optical fiber communication system. The optical fiber communication system includes an optical transmitting device 210, an optical receiving device 220, and an optical fiber link Z. The optical transmitting device 210 and the optical receiving device 220 are connected via the optical fiber link Z. The optical fiber link Z includes multiple sub-optical fiber links 231 and multiple connectors 232, with adjacent sub-optical fiber links 231 connected via connectors 232. The optical fiber link Z can be a bidirectional optical fiber link between the optical transmitting device 210 and the optical receiving device 220, or it can be a unidirectional optical fiber link between the optical transmitting device 210 and the optical receiving device 220. That is, the optical fiber link Z is used for the optical transmitting device 210 to transmit optical signals to the optical receiving device 220 and for the optical receiving device 220 to transmit optical signals to the optical transmitting device 210. Alternatively, the optical fiber link Z is used for the optical transmitting device 210 to transmit optical signals to the optical receiving device 220, but not for the optical receiving device 220 to transmit optical signals to the optical transmitting device 210.

[0139] Optical transmitting device 210 and optical receiving device 220 are collectively referred to as optical communication devices. An optical communication device includes optical modules and / or optical fiber cards, which perform operations related to optical signal processing. Optionally, the optical modules and / or optical fiber cards are pluggable in the optical communication device. For example, the optical communication device includes slots into which the optical modules and / or optical fiber cards are inserted to be installed. In embodiments of this application, the optical communication device may be a network device, a terminal device, or a server. A network device may be an optical transport network device, a switch, or a router, etc. A terminal device may be a personal computer (PC), a desktop computer, a printer, or a camera, etc. For example, optical modules are pluggable in optical transport network devices, switches, routers, or terminal devices, and optical fiber cards are pluggable in optical transport network devices or data communication devices.

[0140] In this embodiment, the optical transmitting device 210 includes any one of a network device, a terminal device, or a server, and the optical receiving device 220 includes any one of a network device, a terminal device, or a server. The optical transmitting device 210 and the optical receiving device 220 can be the same type of optical communication device or different types of optical communication devices. In one example, both the optical transmitting device 210 and the optical receiving device 220 are network devices; for example, both are switches or both are routers. In another example, both the optical transmitting device 210 and the optical receiving device 220 are terminal devices; for example, both are PCs or both are desktop computers. In yet another example, both the optical transmitting device 210 and the optical receiving device 220 are servers. In yet another example, the optical transmitting device 210 is a network device, and the optical receiving device 220 is a terminal device or a server. In yet another example, the optical transmitting device 210 is a terminal device, and the optical receiving device 220 is a network device or a server. In another example, optical transmitting device 210 is a server, and optical receiving device 220 is a network device or terminal device.

[0141] In this embodiment, the optical transmitting device 210 generates a first optical signal carrying a detection sequence and transmits it to the optical receiving device 220 via the optical fiber link Z. After transmission via the optical fiber link Z, the first optical signal becomes a second optical signal, which includes the first optical signal and a reflected optical signal. The reflected optical signal is the optical signal generated by the reflection of the first optical signal in the optical fiber link Z. After receiving the second optical signal via the optical fiber link Z, the optical receiving device 220 demodulates the second optical signal to obtain the detection sequence. Based on the demodulated detection sequence, the optical receiving device 220 determines the transmission performance of the optical fiber link Z. Thus, the optical transmitting device 210 and the optical receiving device 220 cooperate to detect the transmission performance of the optical fiber link Z. This eliminates the need for additional equipment such as OTDRs, circulators (or power dividers) in the optical fiber link Z, and eliminates the need for fiber optic plugging and unplugging. The hardware implementation for detecting the transmission performance of the optical fiber link Z is simple, the detection cost is low, and it enables in-line detection, eliminating the need for on-site personnel to locate faults, thus reducing labor costs.

[0142] The detection sequence can be a pseudo-random binary sequence (PRBS) or a complementary sequence. This detection sequence includes multiple sub-detection sequences, which are multiplexed and carried in the first optical signal. The optical receiving device 220 demodulates the second optical signal to obtain these multiple sub-detection sequences, and determines the transmission performance of the optical fiber link Z based on the demodulated multiple sub-detection sequences. This embodiment uses PRBS or complementary sequences as detection sequences to detect the transmission performance of the optical fiber link Z, which can improve detection sensitivity and increase the detectable distance range. The multiplexing method includes any one of wavelength division multiplexing (WDM), parallel fiber multiplexing, or time division multiplexing (TDM). That is, the detection sequence is carried in the first optical signal using any one of these methods.

[0143] In one embodiment, the multiplexing method is wavelength division multiplexing (WDM). The first optical signal includes multiple sub-optical signals, each corresponding to a specific sub-detection sequence. Each sub-optical signal carries a corresponding sub-detection sequence. Any two sub-optical signals have different wavelengths (i.e., the wavelengths of the multiple sub-optical signals are all different). The optical transmitting device 210 multiplexes these sub-optical signals to obtain the first optical signal. The optical fiber link Z includes a first optical fiber used to transmit the multiple sub-optical signals. For example, the first optical fiber is used to transmit the first optical signal to transmit the multiple sub-optical signals. The optical transmitting device 210 transmits the first optical signal to the optical receiving device 220 via the first optical fiber. The first optical fiber is connected to both the optical transmitting device 210 and the optical receiving device 220. The first optical fiber may include multiple optical fiber segments, each corresponding to a specific sub-optical fiber link 231 included in the optical fiber link Z. Each optical fiber segment is located within its corresponding sub-optical fiber link 231.

[0144] In another embodiment, the multiplexing method is parallel fiber multiplexing. The first optical signal includes multiple sub-optical signals, each corresponding one-to-one with a multiple sub-detection sequence. Each sub-optical signal carries the corresponding sub-detection sequence. The optical fiber link Z includes a first optical fiber and a second optical fiber in parallel. The first optical fiber is used to transmit the first sub-optical signal, and the second optical fiber is used to transmit the second sub-optical signal. The multiple sub-optical signals include the first sub-optical signal and the second sub-optical signal. The optical transmitting device 210 transmits the first sub-optical signal to the optical receiving device 220 through the first optical fiber, and the optical transmitting device 210 transmits the second sub-optical signal to the optical receiving device 220 through the second optical fiber. The first and second optical fibers satisfy the following conditions: the lengths of the first and second optical fibers are the same; and the positions of the connectors on the first and second optical fibers are the same. For example, the first and second optical fibers are encapsulated in the same optical cable, and the connectors on the first and second optical fibers are multiple-fiber push-on / pull-off (MPO) connectors on the optical cable. The first optical fiber is connected to both the optical transmitting device 210 and the optical receiving device 220, and the second optical fiber is also connected to both. The first optical fiber may include multiple optical fiber segments, each corresponding one-to-one with the aforementioned multiple sub-optical fiber links 231 included in the optical fiber link Z, with each segment located within its corresponding sub-optical fiber link 231. Similarly, the second optical fiber may include multiple optical fiber segments, each corresponding one-to-one with the aforementioned multiple sub-optical fiber links 231 included in the optical fiber link Z, with each segment located within its corresponding sub-optical fiber link 231. In a specific embodiment, the optical fiber link Z includes multiple parallel optical fibers, each corresponding one-to-one with the multiple sub-optical signals. Each optical fiber is used to transmit its corresponding sub-optical signal, and the optical transmitting device 210 transmits these sub-optical signals to the optical receiving device 220 through these multiple optical fibers. The multiple optical fibers satisfy the following conditions: they are of the same length; and the connectors on the multiple optical fibers are in the same position. The multiple optical fibers can be encapsulated in the same optical cable, and the connectors on these multiple optical fibers are MPO connectors on the optical cable. Each of the multiple optical fibers is connected to the optical transmitting device 210 and the optical receiving device 220 respectively, and each of the multiple optical fibers includes multiple fiber segments. For each of the multiple optical fibers: the multiple fiber segments in each optical fiber correspond one-to-one with the aforementioned multiple sub-fiber links 231 included in the optical fiber link Z, and each fiber segment is located in the corresponding sub-fiber link 231.

[0145] In another embodiment, the multiplexing method is time-division multiplexing; the first optical signal carries a first sub-detection sequence in a first time period, and the first optical signal carries a second sub-detection sequence in a second time period. The plurality of sub-detection sequences include the first sub-detection sequence and the second sub-detection sequence. For example, the plurality of sub-detection sequences correspond one-to-one with the plurality of time periods, and the first optical signal carries the corresponding sub-detection sequence in each time period. In this further embodiment, the optical fiber link Z may include a single optical fiber or multiple parallel optical fibers. One optical fiber in the optical fiber link Z is used to transmit the first optical signal, and the optical transmitting device 210 transmits the first optical signal to the optical receiving device 220 through one optical fiber in the optical fiber link Z.

[0146] The above is only a general overview of how the first optical signal carries multiple sub-detection sequences in a multiplexed manner. A detailed description of how the first optical signal carries these multiple sub-detection sequences in a multiplexed manner, as well as the corresponding processing operations of the optical receiving device, will be described below and will not be repeated here.

[0147] It should be noted that, Figure 2 The application scenarios shown are for illustrative purposes only and are not intended to limit the technical solutions of this application. The structure of the optical fiber communication system can be adjusted according to actual needs. For example, the length of the optical fiber link Z, the number of connectors 232 included in the optical fiber link Z, the number of sub-optical signals included in the first optical signal, and the number of sub-detection sequences included in the detection sequence can be adjusted according to actual needs.

[0148] Furthermore, the application scenarios of this application embodiment may also include control devices or network management devices, which can be connected to the optical transmitting device 210 and the optical receiving device 220 respectively, and can control the optical transmitting device 210 and the optical receiving device 220. For example, the control device or network management device controls the optical transmitting device 210 to send a first optical signal carrying a detection sequence to the optical receiving device 220 through the optical fiber link Z, controls the optical receiving device 220 to demodulate the second optical signal to obtain the detection sequence, and controls the optical receiving device 220 to determine the transmission performance of the optical fiber link Z based on the demodulated detection sequence, etc. This application embodiment does not limit this aspect.

[0149] The above describes the application scenarios of the embodiments of this application. The method embodiments of this application are described below.

[0150] Please refer to Figure 3 The diagram illustrates a flowchart of a fiber optic link detection method provided in an embodiment of this application. This detection method is performed by a combination of an optical transmitting device and an optical receiving device in a fiber optic communication system. For example, the fiber optic communication system is as follows: Figure 2 As shown, this detection method is performed by the optical transmitting device 210 and the optical receiving device 220 in cooperation. See also Figure 3The detection method includes the following steps S301 to S305.

[0151] S301. The optical transmitting device generates a first optical signal, which carries a detection sequence X. The detection sequence X is used by the optical receiving device to detect the transmission performance of the optical fiber link Z. The detection sequence X includes multiple sub-detection sequences, which are carried in the first optical signal in a multiplexed manner.

[0152] In an optional embodiment, the autocorrelation curve corresponding to the detection sequence X satisfies a preset condition.

[0153] In an optional embodiment, the autocorrelation curve corresponding to the detection sequence X satisfies a preset condition including: the autocorrelation curve corresponding to the detection sequence X has a characteristic peak. Specifically, in a specific embodiment, the autocorrelation curve corresponding to the detection sequence X has only one characteristic peak, and the autocorrelation values ​​at all points on the autocorrelation curve corresponding to the detection sequence X, excluding the characteristic peak, are less than a threshold. That is, the autocorrelation values ​​at all points on the autocorrelation curve corresponding to the detection sequence X, excluding the characteristic peak, are all small (e.g., very small). For example, the autocorrelation curve corresponding to the detection sequence X has only one characteristic peak, and the autocorrelation values ​​at all points on the autocorrelation curve corresponding to the detection sequence X, excluding the characteristic peak, are all 0.

[0154] In this embodiment, the detection sequence X can be a PRBS or a complementary sequence. The autocorrelation curve corresponding to a PRBS has only one characteristic peak, and the autocorrelation values ​​at all points on the PRBS's autocorrelation curve other than the characteristic peak are all small. The autocorrelation curve corresponding to a complementary sequence has only one characteristic peak, and the autocorrelation values ​​at all points on the complementary sequence's autocorrelation curve other than the characteristic peak are all 0. The complementary sequence can be a periodic complementary sequence or an aperiodic complementary sequence. For example, the detection sequence X is a Gray complement sequence. A Gray complement sequence is a pulse-coded sequence and an aperiodic complementary sequence. Since both the autocorrelation curve corresponding to a PRBS and the autocorrelation curve corresponding to a complementary sequence have only one characteristic peak, this embodiment can use a PRBS or a complementary sequence as the detection sequence X.

[0155] In this embodiment, the autocorrelation curve corresponding to the detection sequence X is determined based on the autocorrelation curves of the plurality of sub-detection sequences included in the detection sequence X. Specifically, in this embodiment, the autocorrelation curve corresponding to the detection sequence X is a superposition curve of the autocorrelation curves of the plurality of sub-detection sequences. The position points on the autocorrelation curve corresponding to the detection sequence X correspond one-to-one with the position points on the autocorrelation curves of the plurality of sub-detection sequences. The autocorrelation value of each position point on the autocorrelation curve corresponding to the detection sequence X is equal to the sum of the autocorrelation values ​​of that position point on the autocorrelation curves of the plurality of sub-detection sequences. For example, if the plurality of sub-detection sequences are n sub-detection sequences, where n is an integer greater than 1, the autocorrelation value of each position point on the autocorrelation curve corresponding to the n sub-detection sequences is equal to the sum of the autocorrelation values ​​of the n position points on the n autocorrelation curves of the n sub-detection sequences (the n autocorrelation curves correspond one-to-one with the n sub-detection sequences, and the n position points are located one-to-one on the n autocorrelation curves). Each sub-detection sequence in the plurality of sub-detection sequences has at least one peak in its autocorrelation curve. This at least one peak includes a primary peak and may also include secondary peaks. On the autocorrelation curve of each sub-detection sequence, the peak value of the main peak (i.e., the autocorrelation value of the main peak) is greater than the first threshold, and the peak value of the secondary peak (i.e., the autocorrelation value of the secondary peak) is less than the second threshold. The first threshold is greater than the second threshold, and the difference between the first threshold and the second threshold is greater than a preset difference. The first threshold, the second threshold, and the preset difference can all be set according to actual conditions. That is, on the autocorrelation curve of each sub-detection sequence, the peak value of the main peak is relatively large (e.g., very large), and the peak value of the secondary peak is relatively small (e.g., very small).

[0156] In an optional embodiment, the plurality of sub-detection sequences are of equal length. As an example, the detection sequence X includes four sub-detection sequences, namely sub-detection sequences X1 to X4 (i.e., sub-detection sequence X1, sub-detection sequence X2, sub-detection sequence X3 and sub-detection sequence X4), and the length of each of sub-detection sequences X1 to X4 is 16. Sub-detection sequence X1 is -1,-1,1,-1,-1,-1,-1,1,-1,-1,-1,1,1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1. Then sub-detection sequence X1 is as follows: Figure 4 As shown (the horizontal axis represents the number of symbols included in sub-detection sequence X1, and the vertical axis represents the amplitude of the symbols included in sub-detection sequence X1), sub-detection sequence X2 is as follows: Figure 5As shown (the horizontal axis represents the number of symbols included in sub-detection sequence X2, and the vertical axis represents the amplitude of the symbols included in sub-detection sequence X2), sub-detection sequence X3 is as follows: Figure 6 As shown (the horizontal axis represents the number of symbols included in sub-detection sequence X3, and the vertical axis represents the amplitude of the symbols included in sub-detection sequence X3), sub-detection sequence X4 is as follows: Figure 7 As shown (the horizontal axis represents the number of symbols included in sub-detection sequence X4, and the vertical axis represents the amplitude of the symbols included in sub-detection sequence X4). The autocorrelation curve of sub-detection sequence X1 is shown below. Figure 8 As shown, the autocorrelation curve of the sub-detection sequence X2 is as follows: Figure 9 As shown, the autocorrelation curve of the sub-detection sequence X3 is as follows: Figure 10 As shown, the autocorrelation curve of the sub-detection sequence X4 is as follows: Figure 11 As shown. See also Figures 8 to 11 It can be seen that the autocorrelation curve of each sub-detection sequence X1 to X4 has multiple peaks. These peaks include a main peak (the peak with the largest value on the vertical axis) and at least one secondary peak (peaks other than the main peak). The main peak has a large peak value, while the secondary peaks have very small peak values. Furthermore, the autocorrelation values ​​at all points except the main peak on the autocorrelation curves of sub-detection sequence X1 and X2 are opposite; similarly, the autocorrelation values ​​at all points except the main peak on the autocorrelation curves of sub-detection sequence X3 and X4 are opposite. The autocorrelation curve corresponding to detection sequence X is shown below. Figure 12 As shown, the autocorrelation curve corresponding to the detection sequence X is a superposition curve of the autocorrelation curves of the sub-detection sequences X1 to X4. See also Figure 12 The autocorrelation curve corresponding to the detection sequence X has only one characteristic peak, and the autocorrelation value at all other points on the curve is 0. It should be noted that the first sub-detection sequence can be any sub-detection sequence included in the detection sequence X. The first sub-detection sequence includes multiple symbols. When obtaining the autocorrelation curve of the first sub-detection sequence, one of the two first sub-detection sequences needs to be shifted relative to the other by the sign; the number of symbols shifted is also called the time-shifted symbol number. For example, when obtaining the autocorrelation curve of the sub-detection sequence X1, one of the two sub-detection sequences X1 needs to be shifted relative to the other by the sign. Figures 8 to 12 In the diagram, the horizontal axis represents the number of signs in the time shift, and the vertical axis represents the autocorrelation value (i.e., correlation). Negative and positive numbers indicate different directions of shift. For example, a negative number indicates a shift to the left, while a positive number indicates a shift to the right. The sign count refers to the number of signs.

[0157] In an optional embodiment, the detection sequence X is a Gray complement sequence. There are many methods for generating Gray complement sequences. For example, a Gray complement sequence of length 2L can be generated from a Gray complement sequence of length L, a Gray complement sequence of length 4L can be generated from a Gray complement sequence of length 2L, a Gray complement sequence of length 8L can be generated from a Gray complement sequence of length 4L, and so on.

[0158] For example, Gray complement sequences are generated using the recursive method shown in Equation (1). Higher-order Gray complement sequences (i.e., longer Gray complement sequences) can be generated based on lower-order Gray complement sequences (i.e., shorter Gray complement sequences) and Equation (1).

[0159]

[0160] Equation (1) above expresses the method for generating Gray's complement sequence, which includes four subsequences, A, B, C, and D. In equation (1), the symbol "|" represents concatenation, and "A|B" means placing subsequence B to the right (or after) of subsequence A. This indicates negation of B. For example, if B = 1, then... If B = -1, then Similarly, "C|D" means placing subsequence D to the right (or after) of subsequence C. This indicates negation of D. For example, if D = 1, then... If D = -1, then

[0161] In one example, a Gray complement sequence of length 4 is: The process of generating an 8-length Gray complement sequence from the 4-length Gray complement sequence is shown in equation (2).

[0162]

[0163] The process of generating a Gray complement sequence of length 16 from the Gray complement sequence of length 8 is shown in equation (3) below.

[0164]

[0165] Similarly, higher-order Gray complement sequences can be generated. For example, a Gray complement sequence of length 32 can be generated from a Gray complement sequence of length 16, and a Gray complement sequence of length 64 can be generated from a Gray complement sequence of length 32, and so on. For example, as mentioned above, the sub-detection sequence X1 is -1,-1,1,-1,-1,-1,-1,1,-1,-1,1,-1,1,1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1. According to the above equation (3), the sub-detection sequences X1 to X4 are four sub-sequences of the Gray complement sequence of length 16 expressed by the above equation (3). The detection sequence X can be a Gray complement sequence expressed by equation (3) above or a higher-order Gray complement sequence. In this embodiment, the detection sequence X is taken as a Gray complement sequence expressed by equation (3) above, and the autocorrelation curve corresponding to the detection sequence X is as follows: Figure 12 As shown.

[0166] The above description uses the determination of the autocorrelation curve corresponding to the detection sequence X based on the autocorrelation curves of the sub-detection sequences X1 to X4 as an example, and mainly takes the case where the detection sequence X is a Gray complement sequence as an example. The above description of the autocorrelation curve corresponding to the detection sequence X also applies to the case where the detection sequence X is a pseudo-random code sequence, which will not be repeated in the embodiments of this application.

[0167] In this embodiment, the detection sequence X includes the aforementioned multiple sub-detection sequences carried in a multiplexed manner within the first optical signal. This multiplexing method can include any of the following: wavelength division multiplexing, parallel fiber multiplexing, or time division multiplexing. Depending on the multiplexing method, the first optical signal is different, and the implementation method of generating the first optical signal by the optical transmitting device differs. Three cases are described below.

[0168] The first scenario: The multiplexing method is wavelength division multiplexing (WDM). That is, the multiple sub-detection sequences included in the detection sequence X are carried in the first optical signal in a WDM manner.

[0169] In a specific embodiment, the first optical signal includes multiple sub-optical signals, each corresponding one-to-one with a multiple sub-detection sequences. Each sub-optical signal carries a corresponding sub-detection sequence, and any two sub-optical signals have different wavelengths (i.e., the wavelengths of the multiple sub-optical signals are all different). The optical fiber link Z includes a first optical fiber for transmitting the multiple sub-optical signals. In a specific embodiment, the first optical fiber is used to transmit the first optical signal, which in turn transmits the multiple sub-optical signals included in the first optical signal.

[0170] In this first scenario, the optical transmitting device generating the first optical signal may include: the optical transmitting device generating the plurality of sub-optical signals, each of the plurality of sub-optical signals carrying a corresponding sub-detection sequence; and the optical transmitting device multiplexing the plurality of sub-optical signals to obtain the first optical signal. For example, the optical transmitting device includes an optical multiplexer and a plurality of optical transmitters, each of the plurality of optical transmitters corresponding one-to-one with the plurality of sub-optical signals, each optical transmitter being used to generate a corresponding sub-optical signal, and the optical multiplexer being used to multiplex the plurality of sub-optical signals to obtain the first optical signal.

[0171] Let's take the example of n sub-detection sequences, n sub-optical signals, and n optical transmitters. As an example, the n sub-detection sequences are sub-detection sequences X1 to Xn (i.e., sub-detection sequence X1, sub-detection sequence X2, ..., sub-detection sequence Xn), the n sub-optical signals are sub-optical signals F1 to Fn (i.e., sub-optical signal F1, sub-optical signal F2, ..., sub-optical signal Fn), and the n optical transmitters are optical transmitters 1 to n (i.e., optical transmitter 1, optical transmitter 2, ..., optical transmitter n). The sub-optical signals F1 to Fn correspond one-to-one with the sub-detection sequences X1 to Xn. Please refer to [reference needed]. Figure 13 This diagram illustrates another optical fiber communication system provided in an embodiment of this application. In this optical fiber communication system, the optical transmitting device 210 includes an optical multiplexer and optical transmitters 1 to n. The optical fiber link Z includes a first optical fiber (i.e., optical fiber 1). Optical transmitters 1 to n are respectively connected to the optical multiplexer, and the optical multiplexer is connected to the first optical fiber. Sub-optical signal F1 corresponds to sub-detection sequence X1, and optical transmitter 1 is used to generate sub-optical signal F1 carrying sub-detection sequence X1. Sub-optical signal F2 corresponds to sub-detection sequence X2, and optical transmitter 2 is used to generate sub-optical signal F2 carrying sub-detection sequence X2. And so on. Sub-optical signal Fn corresponds to sub-detection sequence Xn, and optical transmitter n is used to generate sub-optical signal Fn carrying sub-detection sequence Xn. That is, optical transmitters 1 to n are used to generate sub-optical signals F1 to Fn that correspond one-to-one with sub-detection sequences X1 to Xn. The optical multiplexer is used to multiplex the sub-optical signals F1 to Fn to obtain a first optical signal. Figure 13As shown, the optical transmitting device 210 also includes a detection sequence generation unit, which is connected to optical transmitters 1 to n respectively. The detection sequence generation unit is used to generate sub-detection sequences X1 to Xn (i.e., to generate detection sequences X). For example, the detection sequence generation unit generates sub-detection sequence X1 and provides it to optical transmitter 1, so that optical transmitter 1 generates a sub-optical signal F1 carrying sub-detection sequence X1. The detection sequence generation unit generates sub-detection sequence X2 and provides it to optical transmitter 2, so that optical transmitter 2 generates a sub-optical signal F2 carrying sub-detection sequence X2. And so on. The detection sequence generation unit generates sub-detection sequence Xn and provides it to optical transmitter n, so that optical transmitter n generates a sub-optical signal Fn carrying sub-detection sequence Xn. n is an integer greater than 1. In a specific example, n equals 4, and the sub-detection sequences X1 to Xn are the aforementioned sub-detection sequences X1 to X4.

[0172] The second scenario is a parallel-fiber multiplexing method. That is, the multiple sub-detection sequences included in the detection sequence X are carried in the first optical signal in a parallel-fiber multiplexing manner.

[0173] In a specific embodiment, the first optical signal includes multiple sub-optical signals, each corresponding one-to-one with a multiple sub-detection sequence, and each sub-optical signal carries the corresponding sub-detection sequence. The optical fiber link Z includes a first optical fiber and a second optical fiber in parallel. The first optical fiber is used to transmit the first sub-optical signal, and the second optical fiber is used to transmit the second sub-optical signal. The multiple sub-optical signals include both the first and second sub-optical signals. For example, the first and second sub-optical signals can be any two of the multiple sub-optical signals.

[0174] The first and second optical fibers satisfy the following conditions: the lengths of the first and second optical fibers are the same; and the positions of the connectors on the first and second optical fibers are the same. Therefore, the influence of the first optical fiber on the first sub-optical signal is the same as the influence of the second optical fiber on the second sub-optical signal, facilitating the joint detection of the transmission performance of the optical fiber link Z using sub-detection sequences carried by the first and second sub-optical signals. For example, the first and second optical fibers are encapsulated in the same optical cable, and the connectors on the first and second optical fibers are MPO connectors on this cable, thereby improving the integration of the optical fiber link Z and facilitating its deployment and connection. Furthermore, the same MPO connector on this optical cable has the same influence on the first and second optical fibers, thus having the same influence on the first sub-optical signal transmitted in the first fiber and the second sub-optical signal transmitted in the second fiber. The first and second sub-optical signals experience the same physical environment during transmission. For example, if the end face of an MPO connector on the optical cable is dirty or the MPO connector is loose, the MPO connector will have the same influence on the first sub-optical signal transmitted in the first fiber and the second sub-optical signal transmitted in the second fiber.

[0175] In a specific embodiment, the fiber optic link Z comprises multiple parallel optical fibers, each corresponding one-to-one with a plurality of sub-optical signals, with each fiber used to transmit its corresponding sub-optical signal. The multiple optical fibers satisfy the following conditions: they are of equal length; and the connectors on them are in the same position. Therefore, the multiple optical fibers have the same impact on the plurality of sub-optical signals, facilitating the joint detection of the transmission performance of the fiber optic link Z using sub-detection sequences carried by the plurality of sub-optical signals. For example, the multiple optical fibers are encapsulated in the same optical cable, and the connectors on the multiple optical fibers are MPO connectors on the optical cable, thereby improving the integration of the fiber optic link Z and facilitating its deployment and connection. Furthermore, the same MPO connector on the optical cable has the same impact on the multiple optical fibers, thus having the same impact on the plurality of sub-optical signals transmitted in the multiple optical fibers. The plurality of sub-optical signals experience the same physical environment during transmission.

[0176] In this second scenario, the generation of the first optical signal by the optical transmitting device may include: the optical transmitting device generating the plurality of sub-optical signals, each of which carries a corresponding sub-detection sequence. For example, the optical transmitting device includes multiple optical transmitters, and the optical fiber link Z includes multiple parallel optical fibers, with the first fiber and the second fiber being any two of the multiple optical fibers. The plurality of optical transmitters are connected one-to-one with the plurality of optical fibers. Each of the plurality of optical transmitters corresponds to one of the plurality of sub-optical signals, and each optical transmitter is used to generate the corresponding sub-optical signal.

[0177] Let's take the example of n sub-detection sequences, n sub-optical signals, and n optical transmitters. As an example, the n sub-detection sequences are sub-detection sequences X1 to Xn, the n sub-optical signals are sub-optical signals F1 to Fn, and the n optical transmitters are optical transmitters 1 to n. Sub-optical signals F1 to Fn correspond one-to-one with sub-detection sequences X1 to Xn. Please refer to [reference needed]. Figure 14 This diagram illustrates another optical fiber communication system provided in an embodiment of this application. In this optical fiber communication system, the optical transmitting device 210 includes optical transmitters 1 to n, and the optical fiber link Z includes optical fibers 1 to n (the first optical fiber and the second optical fiber can be any two of the optical fibers 1 to n). Optical transmitters 1 to n are connected one-to-one with optical fibers 1 to n. Sub-optical signal F1 corresponds to sub-detection sequence X1, and optical transmitter 1 is used to generate sub-optical signal F1 carrying sub-detection sequence X1. Sub-optical signal F2 corresponds to sub-detection sequence X2, and optical transmitter 2 is used to generate sub-optical signal F2 carrying sub-detection sequence X2. And so on. Sub-optical signal Fn corresponds to sub-detection sequence Xn, and optical transmitter n is used to generate sub-optical signal Fn carrying sub-detection sequence Xn. That is, optical transmitters 1 to n are used to generate sub-optical signals F1 to Fn that correspond one-to-one with sub-detection sequences X1 to Xn. Figure 14 As shown, the optical transmitting device 210 also includes a detection sequence generation unit, which is connected to optical transmitters 1 to n respectively. The detection sequence generation unit is used to generate sub-detection sequences X1 to Xn (i.e., to generate detection sequences X). For example, the detection sequence generation unit generates sub-detection sequence X1 and provides it to optical transmitter 1, so that optical transmitter 1 generates a sub-optical signal F1 carrying sub-detection sequence X1. The detection sequence generation unit generates sub-detection sequence X2 and provides it to optical transmitter 2, so that optical transmitter 2 generates a sub-optical signal F2 carrying sub-detection sequence X2. And so on. The detection sequence generation unit generates sub-detection sequence Xn and provides it to optical transmitter n, so that optical transmitter n generates a sub-optical signal Fn carrying sub-detection sequence Xn. n is an integer greater than 1. In a specific example, n equals 4, and the sub-detection sequences X1 to Xn are the aforementioned sub-detection sequences X1 to X4.

[0178] It should be noted that in the second case described above, the wavelengths of the multiple sub-optical signals that correspond one-to-one with the multiple sub-detection sequences may be the same or different. This application embodiment does not limit whether the wavelengths of the multiple sub-optical signals are the same.

[0179] In optional embodiments, in the first and second cases described above, the plurality of sub-detection sequences (e.g., sub-detection sequences X1 to Xn) include a first sub-detection sequence, and the plurality of sub-optical signals (e.g., sub-optical signals F1 to Fn) include a first sub-optical signal, with the first sub-optical signal corresponding to the first sub-detection sequence. The first sub-optical signal carries a plurality of first sub-detection sequences, which are periodically distributed within the first sub-optical signal. There are boundary markers between adjacent first sub-detection sequences among the plurality of first sub-detection sequences; or, adjacent first sub-detection sequences among the plurality of first sub-detection sequences are consecutive. The first sub-detection sequence is any one of the plurality of sub-detection sequences, and the first sub-optical signal is the sub-optical signal among the plurality of sub-optical signals used to carry the first sub-detection sequence. For example, the first sub-detection sequence is sub-detection sequence X1, and the first sub-optical signal is sub-optical signal F1. Another example: the first sub-detection sequence is sub-detection sequence X2, and the first sub-optical signal is sub-optical signal F2. For example, the first sub-detection sequence is the sub-detection sequence Xn, and the first sub-optical signal is the sub-optical signal Fn.

[0180] In one embodiment, please refer to Figure 15 This illustrates a schematic diagram of the distribution of multiple first sub-detection sequences within the first sub-optical signal. For example... Figure 15 As shown, the first sub-optical signal carries k first sub-detection sequences, which are periodically distributed within the first sub-optical signal. Adjacent first sub-detection sequences are identified by boundary markers (one first sub-detection sequence and one boundary marker per period), where k is a positive integer. The boundary marker can be an idle sequence, which can be a sequence of all zeros (i.e., a sequence with all symbols equal to 0). Alternatively, the boundary marker can be a sequence with an amplitude less than the amplitude of the first sub-detection sequence; for example, the amplitude of the boundary marker might be half the amplitude of the first sub-detection sequence. The length of the boundary marker can be the same as or different from the length of the first sub-detection sequence. For example, the length of the boundary marker can be less than the length of the first sub-detection sequence. A boundary marker with a length of 0 indicates that no boundary marker exists. A boundary marker with a length greater than 0 indicates that adjacent first sub-detection sequences are considered to have boundary markers, and that there is a gap between these adjacent sequences, or that the adjacent first sub-detection sequences are discontinuous.

[0181] In another embodiment, please refer to Figure 16 This illustrates another schematic diagram of the distribution of multiple first sub-detection sequences in the first sub-optical signal. For example... Figure 16As shown, the first sub-optical signal carries k first sub-detection sequences, which are periodically distributed in the first sub-optical signal (one first sub-detection sequence in each period). Adjacent first sub-detection sequences are continuous, there are no boundary markers between adjacent first sub-detection sequences, and there are no gaps between adjacent first sub-detection sequences. k is a positive integer.

[0182] In this embodiment, the first optical signal is transmitted via the optical fiber link Z between the optical transmitting device and the optical receiving device and then becomes a second optical signal. The second optical signal includes the first optical signal and a reflected optical signal R. The reflected optical signal R is the optical signal generated by the reflection of the first optical signal in the optical fiber link Z. For example, the reflected optical signal R is the optical signal generated by multiple (e.g., an even number of) reflections of the first optical signal between reflection points on the optical fiber link Z. The reflection points include connectors, the end face of the laser of the optical transmitting device, etc. The intensity of the reflected optical signal R depends on the reflection intensity of the reflection points. When the first optical signal includes the above-mentioned multiple sub-optical signals, the first sub-optical signal among these multiple sub-optical signals is transmitted via the optical fiber link Z and then becomes a third sub-optical signal. The third sub-optical signal includes the first sub-optical signal and a first sub-reflected optical signal. The first sub-reflected optical signal is the optical signal generated by the reflection of the first sub-optical signal in the optical fiber link Z. The second optical signal includes the third sub-optical signal, and the reflected optical signal R includes the first sub-reflected optical signal. Since the first sub-optical signal carries multiple periodically distributed first sub-detection sequences, the third sub-optical signal also carries multiple periodically distributed first sub-detection sequences. This facilitates the optical receiving device in demodulating the first sub-detection sequences from the third sub-optical signal, and then determining the transmission performance of the fiber optic link Z based on the demodulated first sub-detection sequences. Specifically, if the first sub-optical signal carries only one first sub-detection sequence, then the third sub-optical signal also carries only one first sub-detection sequence. The optical receiving device needs to accurately demodulate this first sub-detection sequence from the third sub-optical signal to determine the transmission performance of the fiber optic link Z. However, if the first sub-optical signal carries multiple periodically distributed first sub-detection sequences, then the third sub-optical signal also carries multiple periodically distributed first sub-detection sequences. The optical receiving device only needs to demodulate any one of these multiple first sub-detection sequences from the third sub-optical signal to determine the transmission performance of the fiber optic link Z. This reduces the difficulty for the optical receiving device in demodulating the first sub-detection sequences from the third sub-optical signal. Furthermore, when there are boundary markers between adjacent first sub-detection sequences carried by the first sub-optical signal, there are also boundary markers between adjacent first sub-detection sequences carried by the third sub-optical signal. These boundary markers can be used by the optical receiving device to determine the start and / or end positions of the first sub-detection sequences in the third sub-optical signal, thereby identifying the first sub-detection sequences carried by the third sub-optical signal. In other words, the optical receiving device can determine (i.e., identify) the first sub-detection sequences carried by the third sub-optical signal based on these boundary markers, thus reducing the difficulty for the optical receiving device to identify the first sub-detection sequences from the third sub-optical signal.

[0183] The above description uses a first sub-detection sequence and a first sub-optical signal as examples. In an optional embodiment, the plurality of sub-detection sequences (e.g., sub-detection sequences X1 to Xn) further include a second sub-detection sequence, and the plurality of sub-optical signals (e.g., sub-optical signals F1 to Fn) further include a second sub-optical signal, which corresponds to the second sub-detection sequence. The second sub-optical signal carries a plurality of second sub-detection sequences, which are periodically distributed in the second sub-optical signal. There are boundary markers between adjacent second sub-detection sequences in the plurality of second sub-detection sequences, or adjacent second sub-detection sequences in the plurality of second sub-detection sequences are continuous. The second sub-optical signal becomes a fourth sub-optical signal after transmission via the optical fiber link Z. The fourth sub-optical signal includes the second sub-optical signal and a second sub-reflected optical signal. The second sub-reflected optical signal is an optical signal generated by the reflection of the second sub-optical signal in the optical fiber link Z. The second optical signal includes the fourth sub-optical signal, and the reflected optical signal R includes the second sub-reflected optical signal. In a specific embodiment, each of the plurality of sub-optical signals carries multiple corresponding sub-detection sequences. Within each sub-optical signal, the multiple sub-detection sequences are periodically distributed, with boundary markers between adjacent sub-detection sequences, or adjacent sub-detection sequences are continuous. After transmission via optical fiber link Z, each of the plurality of sub-optical signals becomes a sub-optical signal comprising each sub-optical signal and its corresponding sub-reflected optical signal. As an example, the plurality of sub-detection sequences are sub-detection sequences X1 to Xn, and the plurality of sub-optical signals are sub-optical signals F1 to Fn, with each sub-optical signal F1 to Fn corresponding one-to-one with a sub-detection sequence X1 to Xn. Sub-optical signal F1 carries multiple sub-detection sequences X1, which are periodically distributed within sub-optical signal F1. There are boundary markers between adjacent sub-detection sequences X1, or adjacent sub-detection sequences X1 are continuous. Sub-optical signal F2 carries multiple sub-detection sequences X2, which are periodically distributed within F2. Adjacent sub-detection sequences X2 are either boundary-marked or consecutive. This pattern continues. Sub-optical signal Fn carries multiple sub-detection sequences Xn, which are periodically distributed within Fn. Adjacent sub-detection sequences Xn are either boundary-marked or consecutive. In an optional embodiment, sub-optical signal F1 is transmitted via optical fiber link Z and becomes sub-optical signal G1. Sub-optical signal G1 includes sub-optical signal F1 and sub-reflected optical signal R1, where R1 is the optical signal generated by reflection of sub-optical signal F1 in optical fiber link Z.Sub-optical signal F2, after being transmitted via fiber optic link Z, becomes sub-optical signal G2. Sub-optical signal G2 includes sub-optical signal F2 and sub-reflected optical signal R2, which is the optical signal generated by the reflection of sub-optical signal F2 in fiber optic link Z. Similarly, sub-optical signal Fn, after being transmitted via fiber optic link Z, becomes sub-optical signal Gn. Sub-optical signal Gn includes sub-optical signal Fn and sub-reflected optical signal Rn, which is the optical signal generated by the reflection of sub-optical signal Fn in fiber optic link Z.

[0184] In optional embodiments, in the first and second cases described above, the optical transmitter generates the sub-optical signal carrying the sub-detection sequence using either direct modulation or external modulation. Direct modulation refers to modulation performed within the light source, specifically by directly controlling the light source (e.g., directly controlling the pump source of a laser) to modulate the optical signal emitted by that light source. Direct modulation is also called internal modulation. External modulation refers to modulation performed outside the light source, specifically by using a modulator to modulate the optical signal emitted by the light source outside the light source. The optical transmitter includes a light source and may also include a modulator. For example, in the first and second cases, the plurality of optical transmitters includes a first optical transmitter, and the first sub-optical signal carrying the first sub-detection sequence is generated by the first optical transmitter. For example, the first optical transmitter is optical transmitter 1, the first sub-optical signal is sub-optical signal F1, and the first sub-detection sequence is sub-detection sequence X1.

[0185] The following describes two implementation methods for the first optical transmitter to generate the first sub-optical signal carrying the first sub-detection sequence.

[0186] The first implementation method involves the first optical transmitter generating a first sub-optical signal carrying a first sub-detection sequence using direct modulation. In other words, the first optical transmitter modulates the first sub-detection sequence into the first sub-optical signal using direct modulation.

[0187] For an example, please refer to Figure 17 This illustrates a schematic diagram of a first optical transmitter generating a first sub-optical signal according to an embodiment of this application. Figure 17 As shown, the first optical transmitter includes a light source, and the first optical transmitter uses a first sub-detection sequence to modulate the driving signal (e.g., driving current) of the light source so that the light source emits a first sub-optical signal carrying the first sub-detection sequence.

[0188] The second implementation method: The first optical transmitter uses external modulation to generate a first sub-optical signal carrying the first sub-detection sequence. That is, the first optical transmitter uses external modulation to modulate the first sub-detection sequence into the first sub-optical signal.

[0189] The first optical transmitter includes a light source. The first optical transmitter modulates the optical signal emitted by the light source using a first sub-detection sequence to obtain a first sub-optical signal carrying the first sub-detection sequence. For an example, please refer to... Figure 18 This illustrates another schematic diagram of the first optical transmitter generating a first sub-optical signal according to an embodiment of this application. For example... Figure 18 As shown, the first optical transmitter includes a light source and a modulator. The modulator modulates the optical signal emitted by the light source using a first sub-detection sequence to obtain a first sub-optical signal carrying the first sub-detection sequence.

[0190] The above description uses the generation of a first sub-optical signal by a first optical transmitter as an example. The first optical transmitter can be one of the aforementioned optical transmitters (e.g., ...). Figure 13 and Figure 14 The implementation method of generating the corresponding sub-optical signal by each of the n optical transmitters shown can be referred to the implementation method of generating the first sub-optical signal by the first optical transmitter, which will not be elaborated here.

[0191] The third scenario is time-division multiplexing. That is, the multiple sub-detection sequences included in the detection sequence X are carried in the first optical signal in a time-division multiplexing manner.

[0192] In a specific embodiment, the plurality of sub-detection sequences includes a first sub-detection sequence and a second sub-detection sequence. The first optical signal carries the first sub-detection sequence in a first time period and carries the second sub-detection sequence in a second time period. The first and second sub-detection sequences can be any two of the plurality of sub-detection sequences. The length of the first time period and the length of the second time period can be equal or unequal. For example, the length of both the first and second time periods can be 1 second, 2 seconds, or 3 seconds, etc. In an optional embodiment, the plurality of sub-detection sequences correspond one-to-one with the plurality of time periods, and the first optical signal carries the corresponding sub-detection sequence in each time period. The lengths of the plurality of time periods can be equal or unequal. For example, the lengths of all the plurality of time periods can be 1 second, 2 seconds, or 3 seconds, etc.

[0193] In this third scenario, the optical transmitting device generates a first optical signal. For example, the optical transmitting device includes an optical transmitter connected to an optical fiber link Z, which is used to generate the first optical signal. In a specific embodiment, the optical transmitter generates a first optical signal carrying a first sub-detection sequence in a first time period, and the optical transmitter generates a first optical signal carrying a second sub-detection sequence in a second time period.

[0194] Let's take the example of n sub-detection sequences. These n sub-detection sequences are sub-detection sequences X1 to Xn, and each sub-detection sequence X1 to Xn corresponds one-to-one with a time period T1 to Tn (the first time period and the second time period can be any two time periods from T1 to Tn). Please refer to [reference needed]. Figure 19 This diagram illustrates another optical fiber communication system provided in an embodiment of this application. In this optical fiber communication system, the optical transmitting device 210 includes an optical transmitter connected to an optical fiber link Z. A sub-detection sequence X1 corresponds to a time period T1, and the optical transmitter is used to generate a first optical signal carrying the sub-detection sequence X1 during time period T1 (i.e., the first optical signal carries the sub-detection sequence X1 during time period T1). A sub-detection sequence X2 corresponds to a time period T2, and the optical transmitter is used to generate a first optical signal carrying the sub-detection sequence X2 during time period T2 (i.e., the first optical signal carries the sub-detection sequence X2 during time period T2). And so on. A sub-detection sequence Xn corresponds to a time period Tn, and the optical transmitter is used to generate a first optical signal carrying the sub-detection sequence Xn during time period Tn (i.e., the first optical signal carries the sub-detection sequence Xn during time period Tn). Figure 19 As shown, the optical transmitting device 210 further includes a detection sequence generation unit connected to the optical transmitter. The detection sequence generation unit is used to generate sub-detection sequences X1 to Xn (i.e., to generate detection sequence X). In a specific embodiment, the detection sequence generation unit generates sub-detection sequence X1 and provides it to the optical transmitter during time period T1, so that the optical transmitter generates a first optical signal carrying sub-detection sequence X1 during time period T1. The detection sequence generation unit generates sub-detection sequence X2 and provides it to the optical transmitter during time period T2, so that the optical transmitter generates a first optical signal carrying sub-detection sequence X2 during time period T2. And so on. The detection sequence generation unit generates sub-detection sequence Xn and provides it to the optical transmitter during time period Tn, so that the optical transmitter generates a first optical signal carrying sub-detection sequence Xn during time period Tn. n is an integer greater than 1. In a specific example, n equals 4, and the sub-detection sequences X1 to Xn are the aforementioned sub-detection sequences X1 to X4.

[0195] In an optional embodiment, in this third case, the first optical signal carries multiple first sub-detection sequences in a first time period. These multiple first sub-detection sequences are periodically distributed within the first optical signal, and there are boundary markers between adjacent first sub-detection sequences; or, adjacent first sub-detection sequences are consecutive. The implementation of the first optical signal carrying the multiple first sub-detection sequences in the first time period can be found in [reference needed]. Figure 15 or Figure 16This will not be elaborated upon here. As mentioned earlier, the first optical signal is transformed into a second optical signal after transmission via the fiber optic link Z. The second optical signal includes the first optical signal and the reflected optical signal R. Since the first optical signal carries multiple periodically distributed first sub-detection sequences in the first time period, the second optical signal also carries multiple periodically distributed first sub-detection sequences. This facilitates the optical receiving device in demodulating the first sub-detection sequences from the second optical signal, and then determining the transmission performance of the fiber optic link Z based on the demodulated first sub-detection sequences. Specifically, if the first optical signal carries only one first sub-detection sequence, then the second optical signal also carries only one first sub-detection sequence. The optical receiving device needs to accurately demodulate this first sub-detection sequence from the second optical signal in order to determine the transmission performance of the fiber optic link Z based on the demodulated first sub-detection sequence. If the first optical signal carries multiple periodically distributed first sub-detection sequences, then the second optical signal also carries multiple periodically distributed first sub-detection sequences. The optical receiving device only needs to demodulate any one of these first sub-detection sequences from the second optical signal to determine the transmission performance of the fiber optic link Z based on the demodulated first sub-detection sequence. This reduces the difficulty for the optical receiving device to demodulate the first sub-detection sequences from the second optical signal. Furthermore, if there are boundary markers between adjacent first sub-detection sequences carried by the first optical signal, there are also boundary markers between adjacent first sub-detection sequences carried by the second optical signal. These boundary markers are used by the optical receiving device to determine the start and / or end positions of the first sub-detection sequences in the second optical signal, thereby identifying the first sub-detection sequences carried by the second optical signal. In other words, the optical receiving device can identify the first sub-detection sequences carried by the second optical signal based on these boundary markers, thus reducing the difficulty for the optical receiving device to identify the first sub-detection sequences from the second optical signal.

[0196] The above description uses a first sub-detection sequence and a first time period as an example. In an optional embodiment, the first optical signal carries multiple second sub-detection sequences in a second time period. These multiple second sub-detection sequences are periodically distributed in the first optical signal, and there are boundary markers between adjacent second sub-detection sequences; or, adjacent second sub-detection sequences are continuous. In a specific embodiment, the multiple sub-detection sequences correspond one-to-one with multiple time periods. The first optical signal carries multiple corresponding sub-detection sequences in each time period. In each time period, the multiple sub-detection sequences are periodically distributed, and there are boundary markers between adjacent sub-detection sequences; or, adjacent sub-detection sequences are continuous. As an example, the multiple sub-detection sequences are sub-detection sequences X1 to Xn, and the multiple time periods are time periods T1 to Tn, with each sub-detection sequence X1 to Xn corresponding one-to-one with each time period T1 to Tn. The first optical signal carries multiple sub-detection sequences X1 in time period T1. These multiple sub-detection sequences X1 are periodically distributed in the first optical signal, and there are boundary markers between adjacent sub-detection sequences X1, or adjacent sub-detection sequences X1 are continuous. The first optical signal carries multiple sub-detection sequences X2 in time period T2. These multiple sub-detection sequences X2 are periodically distributed in the first optical signal, and there are boundary markers between adjacent sub-detection sequences X2, or adjacent sub-detection sequences X2 are continuous. And so on. The first optical signal carries multiple sub-detection sequences Xn in time period Tn. These multiple sub-detection sequences Xn are periodically distributed in the first optical signal, and there are boundary markers between adjacent sub-detection sequences Xn, or adjacent sub-detection sequences Xn are continuous.

[0197] In an optional embodiment, in the third case described above, the optical transmitter generates a signal carrying the first optical signal using either direct modulation or external modulation. The specific implementation method can be found in the implementation method of the first optical transmitter generating the first sub-optical signal, and will not be elaborated here.

[0198] In optional embodiments, in the first to third cases described above, the first optical signal also carries a data signal (i.e., the first optical signal carries the detection sequence X and the data signal). In this way, the embodiments of this application can achieve the transmission performance of the in-path detection fiber optic link Z. When the first optical signal carries the detection sequence X and the data signal, the detection sequence X and the data signal may be carried in different fields, or the detection sequence may be modulated onto the data signal (the detection sequence X and the data signal may be carried in the same field). The embodiments of this application do not limit this to any particular case.

[0199] In an optional embodiment, the first optical signal carries a detection sequence X and a data signal. The detection sequence X is modulated onto the data signal, with the modulation depth of the detection sequence X being less than the modulation depth of the data signal, and the baud rate of the detection sequence X being less than the baud rate of the data signal. For example, the ratio of the modulation depth of the detection sequence X to the modulation depth of the data signal is less than a preset ratio, and the difference between the baud rate of the detection sequence X and the baud rate of the data signal is within a preset range. Both the preset ratio and the preset range can be set according to actual conditions. For example, the preset ratio is 0.1, and the preset range is from several MHz (megahertz) to several GHz (gigahertz). Since the detection sequence X is considered noise for the data signal, this embodiment designs the modulation depth of the detection sequence X to be less than the modulation depth of the data signal, and the baud rate of the detection sequence X to be less than the baud rate of the data signal. This achieves the transmission performance of the fiber optic link Z with in-path detection while preventing the detection sequence X from affecting the data signal. In addition, the difference between the baud rate of the detection sequence X and the baud rate of the data signal is within a preset range, which can prevent the detection sequence X from affecting the data signal, while also preventing the detection sequence X from having too low a baud rate, which would make it difficult to detect the transmission performance of the fiber optic link Z.

[0200] In optional embodiments, in the first and second cases described above, at least one of the plurality of sub-optical signals carries a data signal (i.e., carries a data signal and a corresponding sub-detection sequence). In each of these at least one sub-optical signals: the sub-detection sequence and the data signal are carried in different fields (e.g., each sub-optical signal carries the sub-detection sequence and the data signal in a time-division multiplexing manner), or the sub-detection sequence is modulated over the data signal (the sub-detection sequence and the data signal are carried in the same field). In one embodiment, in each of these at least one sub-optical signals: the sub-detection sequence is modulated over the data signal, the modulation depth of the sub-detection sequence is less than the modulation depth of the data signal, and the baud rate of the sub-detection sequence is less than the baud rate of the data signal. This allows for achieving the transmission performance of the in-path detection fiber link Z while preventing the sub-detection sequence from affecting the data signal. For example, in each of these at least one sub-optical signals: the sub-detection sequence is modulated over the data signal, the ratio of the modulation depth of the sub-detection sequence to the modulation depth of the data signal is less than the aforementioned preset ratio, and the difference between the baud rate of the sub-detection sequence and the baud rate of the data signal is within the aforementioned preset range. In this application, for any one of the at least one sub-optical signals, the corresponding optical transmitter can use direct modulation to modulate the data signal into the sub-optical signal, or it can use external modulation to modulate the data signal into the sub-optical signal. This application does not limit this.

[0201] For example, in the first and second cases described above, the first sub-optical signal also carries a data signal (for example, the data signal carried by the first sub-optical signal is referred to as the first data signal). That is, the first sub-optical signal carries the first sub-detection sequence and the first data signal. Continuing with the example of the first optical transmitter generating the first sub-optical signal, four implementation methods for the first optical transmitter to generate the first sub-optical signal are introduced below.

[0202] The first implementation method involves the first optical transmitter using direct modulation to modulate the first sub-detection sequence and the first data signal into a first sub-optical signal. In other words, the first optical transmitter uses direct modulation to generate the first sub-optical signal carrying the first sub-detection sequence and the first data signal.

[0203] The first optical transmitter includes a light source, which modulates a driving signal (e.g., driving current) of the light source with a first sub-detection sequence and a first data signal to cause the light source to emit a first sub-optical signal carrying the first sub-detection sequence and the first data signal.

[0204] For an example, please refer to Figure 20 This illustrates yet another schematic diagram of the first optical transmitter generating a first sub-optical signal according to an embodiment of this application. For example... Figure 20 As shown, the first optical transmitter includes a light source. The first optical transmitter sequentially modulates the driving signal of the light source with a first data signal and a first sub-detection sequence, so that the light source emits a first sub-optical signal carrying the first sub-detection sequence and the first data signal.

[0205] Figure 20 The following example illustrates the process of a first optical transmitter modulating a light source's driving signal using a first data signal, and then modulating the same driving signal using a first sub-detection sequence. In some embodiments, the first optical transmitter first modulates the light source's driving signal using a first sub-detection sequence, and then modulates the same driving signal using the first data signal. In other embodiments, such as... Figure 21 As shown, the first optical transmitter modulates the first sub-detection sequence onto the first data signal. The first optical transmitter uses the first data signal modulated with the first sub-detection sequence to modulate the driving signal of the light source, so that the light source emits a first sub-optical signal carrying the first sub-detection sequence and the first data signal.

[0206] The second implementation method: The first optical transmitter uses external modulation to modulate the first sub-detection sequence and the first data signal into the first sub-optical signal. That is, the first optical transmitter uses external modulation to generate the first sub-optical signal carrying the first sub-detection sequence and the first data signal.

[0207] The first optical transmitter includes a light source. The first optical transmitter modulates the optical signal emitted by the light source using a first sub-detection sequence and a first data signal to obtain a first sub-optical signal carrying the first sub-detection sequence and the first data signal.

[0208] For an example, please refer to Figure 22 This illustrates yet another schematic diagram of the first optical transmitter generating a first sub-optical signal according to an embodiment of this application. For example... Figure 22 As shown, the first optical transmitter includes a light source, modulator 1, and modulator 2. Modulator 1 modulates the optical signal emitted by the light source using a first data signal to obtain a first sub-optical signal carrying the first data signal. The first sub-optical signal modulated by modulator 1 is then transmitted into modulator 2. Modulator 2 modulates the first sub-optical signal carrying the first data signal using a first sub-detection sequence to obtain a first sub-optical signal carrying both the first sub-detection sequence and the first data signal. That is, the first optical transmitter sequentially modulates the optical signal emitted by the light source using the first data signal and the first sub-detection sequence to obtain the first sub-optical signal carrying both the first sub-detection sequence and the first data signal.

[0209] Figure 22 The following example illustrates the process of a first optical transmitter modulating an optical signal using a first data signal, and then modulating the optical signal using a first sub-detection sequence. In some embodiments, the first optical transmitter first modulates the optical signal using a first sub-detection sequence, and then modulates the optical signal using the first data signal. In other embodiments, such as... Figure 23 As shown, the first optical transmitter modulates the first sub-detection sequence onto the first data signal. The first optical transmitter uses the first data signal modulated with the first sub-detection sequence to modulate the optical signal emitted by the light source to obtain a first sub-optical signal carrying the first sub-detection sequence and the first data signal.

[0210] The third implementation method: The first optical transmitter uses direct modulation to modulate the first sub-detection sequence into the first sub-optical signal, and the first optical transmitter uses external modulation to modulate the first data signal into the first sub-optical signal. That is, the first optical transmitter uses both direct modulation and external modulation to generate the first sub-optical signal carrying the first sub-detection sequence and the first data signal.

[0211] The first optical transmitter includes a light source. The first optical transmitter modulates the driving signal of the light source with a first sub-detection sequence so that the light source emits a first sub-optical signal carrying the first sub-detection sequence. The first optical transmitter modulates the first sub-optical signal carrying the first sub-detection sequence emitted by the light source with a first data signal so as to obtain a first sub-optical signal carrying the first sub-detection sequence and the first data signal.

[0212] For an example, please refer to Figure 24This illustrates yet another schematic diagram of the first optical transmitter generating a first sub-optical signal according to an embodiment of this application. For example... Figure 24 As shown, the first optical transmitter includes a light source and a modulator. The first optical transmitter modulates the driving signal of the light source with a first sub-detection sequence so that the light source emits a first sub-optical signal carrying the first sub-detection sequence. The first sub-optical signal carrying the first sub-detection sequence emitted by the light source is injected into the modulator. The modulator modulates the first sub-optical signal carrying the first sub-detection sequence with a first data signal so as to obtain a first sub-optical signal carrying the first sub-detection sequence and the first data signal.

[0213] The fourth implementation method: The first optical transmitter uses direct modulation to modulate the first data signal into the first sub-optical signal, and the first optical transmitter uses external modulation to modulate the first sub-detection sequence into the first sub-optical signal. That is, the first optical transmitter uses both direct modulation and external modulation to generate the first sub-optical signal carrying the first sub-detection sequence and the first data signal.

[0214] The first optical transmitter includes a light source. The first optical transmitter uses a first data signal to modulate the driving signal of the light source so that the light source emits a first sub-optical signal carrying the first data signal. The first optical transmitter uses a first sub-detection sequence to modulate the first sub-optical signal carrying the first data signal emitted by the light source so as to obtain a first sub-optical signal carrying the first sub-detection sequence and the first data signal.

[0215] For an example, please refer to Figure 25 This illustrates yet another schematic diagram of the first optical transmitter generating a first sub-optical signal according to an embodiment of this application. For example... Figure 25 As shown, the first optical transmitter includes a light source and a modulator. The first optical transmitter uses a first data signal to modulate the driving signal of the light source so that the light source emits a first sub-optical signal carrying the first data signal. The first sub-optical signal carrying the first data signal emitted by the light source is injected into the modulator. The modulator uses a first sub-detection sequence to modulate the first sub-optical signal carrying the first data signal so as to obtain a first sub-optical signal carrying the first sub-detection sequence and the first data signal.

[0216] In an optional embodiment, for Figure 20 , Figure 21 and Figure 23 The modulation scheme shown indicates that the first sub-optical signal can be expressed using equation (4). For Figure 22 , Figure 24 and Figure 25 The modulation scheme shown can be expressed by the following formula (5).

[0217] P(t) = (P0(t) + E) * (1 + m * Patt)detect Equation (4).

[0218] P(t)=P0(t)+m*Patt detect Equation (5).

[0219] Where P0(t) represents the first data signal, Patt detect Let P0(t) represent the first sub-detection sequence, m represent the ratio of the modulation depth of the first sub-detection sequence to the modulation depth of the first data signal (when the modulation depth of the first data signal is 1, m represents the modulation depth of the first sub-detection sequence), E is a constant DC bias, E is a constant, and the existence of E is to make P0(t)+E greater than 0. The symbol "*" represents the multiplication sign.

[0220] It should be noted that, in the case where the first sub-optical signal carries the first sub-detection sequence and the first data signal, the above description (e.g.) Figures 20 to 25 This is illustrated using the example of a first sub-optical signal simultaneously carrying a first sub-detection sequence and a first data signal. In the above description (e.g.) Figures 20 to 25 In this embodiment, the first sub-detection sequence and the first data signal are carried in the same field, and the first sub-detection sequence is modulated onto the first data signal. In other embodiments, the first sub-optical signal can carry the first sub-detection sequence and the first data signal in a time-division multiplexing manner, with the first sub-detection sequence and the first data signal carried in different fields. That is, the first sub-optical signal carries the first sub-detection sequence and the first data signal in a time-division multiplexing manner. In a specific embodiment, the first sub-optical signal carries the first sub-detection sequence in a certain time period and carries the first data signal in another time period. In this case, the first optical transmitter generates the first sub-optical signal carrying the first sub-detection sequence in the certain time period and generates the first sub-optical signal carrying the first data signal in the other time period. The implementation method of the first optical transmitter generating the first sub-optical signal carrying the first sub-detection sequence in the certain time period can be referred to Figure 17 and Figure 18 The implementation method of the first optical transmitter generating the first sub-optical signal carrying the first data signal in another time period, as described above, can be found in [reference needed]. Figure 17 and Figure 18 Its description is omitted here.

[0221] The above description uses the generation of a first sub-optical signal by a first optical transmitter as an example. The first optical transmitter can be one of the aforementioned optical transmitters (e.g., ...). Figure 13 and Figure 14 The implementation method of generating the corresponding sub-optical signal by each of the n optical transmitters shown can be referred to the implementation method of generating the first sub-optical signal by the first optical transmitter, which will not be elaborated here.

[0222] In an optional embodiment, in the third case described above, the first optical signal also carries a data signal (i.e., the first optical signal carries the detection sequence X and the data signal), and the detection sequence X and the data signal are carried in different fields (e.g., the first optical signal carries the detection sequence X and the data signal in a time-division multiplexing manner), or the detection sequence X is modulated onto the data signal (the detection sequence X and the data signal are carried in the same field). In one embodiment, the detection sequence X is modulated onto the data signal, the modulation depth of the detection sequence X is less than the modulation depth of the data signal, and the baud rate of the detection sequence X is less than the baud rate of the data signal. For example, the ratio of the modulation depth of the detection sequence X to the modulation depth of the data signal is less than the aforementioned preset ratio, and the difference between the baud rate of the detection sequence X and the baud rate of the data signal is within the aforementioned preset range. In one embodiment, a first optical signal carries a first sub-detection sequence and a first data signal in a first time period. The first sub-detection sequence is modulated onto the first data signal, and the modulation depth of the first sub-detection sequence is less than the modulation depth of the first data signal, and the baud rate of the first sub-detection sequence is less than the baud rate of the first data signal. In a second time period, the first optical signal carries a second sub-detection sequence and a second data signal. The second sub-detection sequence is modulated onto the second data signal, and the modulation depth of the second sub-detection sequence is less than the modulation depth of the second data signal, and the baud rate of the second sub-detection sequence is less than the baud rate of the second data signal. In an optional embodiment, the detection sequence X includes sub-detection sequences X1 to Xn, which correspond one-to-one with time periods T1 to Tn. The first optical signal carries a data signal and a corresponding sub-detection sequence in each time period. The sub-detection sequence is modulated onto the data signal, and the modulation depth of the sub-detection sequence is less than the modulation depth of the data signal, and the baud rate of the sub-detection sequence is less than the baud rate of the data signal. The specific implementation of the first optical signal carrying the detection sequence X (or sub-detection sequence) and the data signal can refer to the specific implementation of the first sub-optical signal carrying the first sub-detection sequence and the first data signal. In the third scenario described above, the method by which the optical transmitter generates the first optical signal can be referenced from the method by which the first optical transmitter generates the first sub-optical signal, and will not be elaborated upon here.

[0223] It should be noted that the light source mentioned above can be any possible light source such as a laser or a laser diode (LD). The laser can include any one of a vertical cavity surface emitting laser (VCSEL), an electro-absorption modulated laser (EML), or a directly modulated laser (DML). The modulator can be any possible modulator such as a Mach-Zehnder modulator (MZM) or an electrically variable optical attenuator (EVOA), and the embodiments of this application do not limit this.

[0224] In an optional embodiment, the baud rates of the plurality of sub-detection sequences in the first optical signal are equal. For example, the first optical signal includes a plurality of sub-optical signals, each of which carries one of the plurality of sub-detection sequences, and the baud rates of the plurality of sub-detection sequences are equal.

[0225] S302. The optical transmitting device sends the first optical signal to the optical receiving device through the optical fiber link Z.

[0226] To simplify the description and facilitate understanding, the implementation processes of S302 and S303 are described together in this embodiment. Therefore, the implementation process of S302 will not be elaborated here; please refer to the relevant description in S303 for the implementation process of S302.

[0227] S303. The optical receiving device receives a second optical signal through the optical fiber link Z. The second optical signal includes the first optical signal and the reflected optical signal R.

[0228] An optical transmitting device sends a first optical signal to an optical receiving device via fiber optic link Z. The first optical signal is transformed into a second optical signal after transmission via fiber optic link Z, and the optical receiving device receives the second optical signal via fiber optic link Z. The second optical signal includes the first optical signal and a reflected optical signal R. The first optical signal is generated by the optical transmitting device, and the reflected optical signal R is generated by the reflection of the first optical signal in fiber optic link Z. For example, the reflected optical signal R is generated by multiple (e.g., an even number of) reflections of the first optical signal between reflection points on fiber optic link Z. Reflection points include connectors, the end face of the laser of the optical transmitting device, etc. The intensity of the reflected optical signal R depends on the reflection intensity of the reflection points. The first optical signal carries a detection sequence X, and the multiple sub-detection sequences included in detection sequence X are carried in the first optical signal in a multiplexed manner. Therefore, the second optical signal carries the detection sequence X, and the multiple sub-detection sequences included in detection sequence X are carried in the second optical signal in a multiplexed manner.

[0229] The multiplexing method includes any one of wavelength division multiplexing, parallel fiber multiplexing, or time division multiplexing. Depending on the multiplexing method, the first optical signal is different, the second optical signal is different, the process of the optical transmitting device sending the first optical signal to the optical receiving device through fiber optic link Z is different, and the process of the optical receiving device receiving the second optical signal through fiber optic link Z is different. The implementation processes of S302 and S303 are described below in three cases.

[0230] The first scenario (corresponding to the first scenario in S301): The multiplexing method is wavelength division multiplexing (WDM). The first optical signal includes multiple sub-optical signals, each corresponding one-to-one with the multiple sub-detection sequences included in the detection sequence X. Each sub-optical signal carries its corresponding sub-detection sequence. The first optical signal is obtained by multiplexing these multiple sub-optical signals using an optical transmitting device. The optical fiber link Z includes a first optical fiber used to transmit these multiple sub-optical signals. For example, the first optical fiber is used to transmit the first optical signal in order to transmit these multiple sub-optical signals. The optical transmitting device sends the first optical signal to the optical receiving device through the first optical fiber, and the optical receiving device receives the second optical signal through the first optical fiber.

[0231] In the first scenario, since the first optical signal comprises multiple sub-optical signals, it is transformed into a second optical signal after transmission via fiber optic link Z. The second optical signal includes the first optical signal and a reflected optical signal R. Therefore, the second optical signal also comprises multiple sub-optical signals. For ease of distinction, the sub-optical signals included in the first optical signal are referred to as transmitted sub-optical signals, and the sub-optical signals included in the second optical signal are referred to as received sub-optical signals. The first optical signal comprises multiple transmitted sub-optical signals, and the second optical signal comprises multiple received sub-optical signals. The multiple received sub-optical signals included in the second optical signal correspond one-to-one with the multiple transmitted sub-optical signals included in the first optical signal. Each received sub-optical signal includes a corresponding transmitted sub-optical signal and a sub-reflected optical signal generated by the reflection of the corresponding transmitted sub-optical signal in fiber optic link Z. The reflected optical signal R includes the sub-reflected optical signals among the multiple received sub-optical signals (that is, the reflected optical signal R includes the sub-reflected optical signals generated by the reflection of each of the multiple transmitted sub-optical signals in fiber optic link Z). It is understood that the first sub-optical signal and the second sub-optical signal mentioned in S301 for the first case refer to the two transmitting sub-optical signals included in the first optical signal. After being transmitted via fiber optic link Z, the first sub-optical signal becomes the third sub-optical signal, which includes the first sub-optical signal and the first sub-reflected optical signal. After being transmitted via fiber optic link Z, the second sub-optical signal becomes the fourth sub-optical signal, which includes the second sub-optical signal and the second sub-reflected optical signal. The third and fourth sub-optical signals are the two receiving sub-optical signals included in the second optical signal. The first sub-reflected optical signal and the second sub-reflected optical signal are the two sub-reflected optical signals included in the reflected optical signal R.

[0232] As an example, the first optical signal includes the aforementioned multiple sub-optical signals (i.e., transmitted sub-optical signals) which are sub-optical signals F1 to Fn, and the detection sequence X includes the aforementioned multiple sub-detection sequences which are sub-detection sequences X1 to Xn. Sub-optical signals F1 to Fn correspond one-to-one with sub-detection sequences X1 to Xn. After being transmitted via optical fiber link Z, sub-optical signals F1 to Fn become sub-optical signals G1 to Gn. Sub-optical signals G1 to Gn are the multiple received sub-optical signals included in the second optical signal, and sub-optical signals G1 to Gn correspond one-to-one with sub-optical signals F1 to Fn. Sub-optical signal G1 includes sub-optical signal F1 and sub-reflected optical signal R1, sub-optical signal G2 includes sub-optical signal F2 and sub-reflected optical signal R2, and so on. Sub-optical signal Gn includes sub-optical signal Fn and sub-reflected optical signal Rn. The reflected optical signal R includes sub-reflected optical signals R1 to Rn. Figure 13As shown, the optical transmitting device 210 includes optical transmitters 1-n and an optical multiplexer, the optical receiving device 220 includes an optical demultiplexer, and the optical fiber link Z includes a first optical fiber. The optical multiplexer is connected to the optical transmitters 1-n respectively, and both the optical multiplexer and the optical demultiplexer are connected to the first optical fiber. The optical transmitters 1-n generate sub-optical signals F1-Fn in a one-to-one correspondence, and each sub-optical signal F1-Fn carries a sub-detection sequence X1-Xn (that is, sub-optical signal F1 carries sub-detection sequence X1, sub-optical signal F2 carries sub-detection sequence X2, and so on, with sub-optical signal Fn carrying sub-detection sequence Xn). The optical multiplexer multiplexes the sub-optical signals F1-Fn to obtain a first optical signal, which is then transmitted to the optical receiving device 220 through the first optical fiber. After transmission through the first optical fiber, the first optical signal becomes a second optical signal, which is received by the optical demultiplexer through the first optical fiber. The second optical signal includes sub-optical signals G1-Gn.

[0233] The second scenario (corresponding to the second scenario in S301): The multiplexing method is parallel fiber multiplexing. The first optical signal includes multiple sub-optical signals, each corresponding one-to-one with the multiple sub-detection sequences included in the detection sequence X. Each sub-optical signal carries its corresponding sub-detection sequence. The optical fiber link Z includes a first optical fiber and a second optical fiber in parallel. The first optical fiber is used to transmit the first sub-optical signal, and the second optical fiber is used to transmit the second sub-optical signal. The multiple sub-optical signals include both the first and second sub-optical signals. The optical transmitting device transmits the first sub-optical signal to the optical receiving device through the first optical fiber, and the optical transmitting device transmits the second sub-optical signal to the optical receiving device through the second optical fiber. The first sub-optical signal becomes a third sub-optical signal after transmission through the first optical fiber, and the second sub-optical signal becomes a fourth sub-optical signal after transmission through the second optical fiber. The optical receiving device receives the third sub-optical signal through the first optical fiber, and the optical receiving device receives the fourth sub-optical signal through the second optical fiber. The third sub-optical signal includes the first sub-optical signal and a first reflected sub-optical signal. The first reflected sub-optical signal is the optical signal generated by the reflection of the first sub-optical signal in the optical fiber link Z (specifically, the first optical fiber). The fourth sub-optical signal includes the second sub-optical signal and the second reflected sub-optical signal. The second reflected sub-optical signal is the optical signal generated by the reflection of the second sub-optical signal in the optical fiber link Z (specifically, the second optical fiber). The second optical signal includes the third and fourth sub-optical signals, and the reflected optical signal R includes the first and second reflected sub-optical signals.

[0234] In the second scenario, since the first optical signal comprises multiple sub-optical signals, it transforms into a second optical signal after transmission via fiber optic link Z. The second optical signal includes both the first optical signal and a reflected optical signal R. Therefore, the second optical signal also comprises multiple sub-optical signals. For ease of distinction, the sub-optical signals included in the first optical signal are referred to as transmitted sub-optical signals, and the sub-optical signals included in the second optical signal are referred to as received sub-optical signals. The first optical signal comprises multiple transmitted sub-optical signals, and the second optical signal comprises multiple received sub-optical signals. Each received sub-optical signal corresponds one-to-one with the transmitted sub-optical signals included in the first optical signal. Each received sub-optical signal includes a corresponding transmitted sub-optical signal and a sub-reflected optical signal generated by the reflection of that corresponding transmitted sub-optical signal in fiber optic link Z. The reflected optical signal R includes the sub-reflected optical signals from among the multiple received sub-optical signals (i.e., the reflected optical signal R includes the sub-reflected optical signals generated by the reflection of each of the multiple transmitted sub-optical signals in fiber optic link Z). The first and second sub-optical signals are two transmitting sub-optical signals included in the first optical signal, and the third and fourth sub-optical signals are two receiving sub-optical signals included in the second optical signal. In a specific embodiment, the optical fiber link Z includes multiple parallel optical fibers, each corresponding one-to-one with one of the multiple transmitting sub-optical signals included in the first optical signal; the optical transmitting device transmits the multiple transmitting sub-optical signals to the optical receiving device through the multiple optical fibers, and the multiple transmitting sub-optical signals are transformed into multiple receiving sub-optical signals after transmission through the multiple optical fibers; the optical receiving device receives the multiple receiving sub-optical signals through the multiple optical fibers.

[0235] As an example, the first optical signal includes the aforementioned multiple sub-optical signals (i.e., transmitted sub-optical signals) which are sub-optical signals F1 to Fn, and the detection sequence X includes the aforementioned multiple sub-detection sequences which are sub-detection sequences X1 to Xn. Sub-optical signals F1 to Fn correspond one-to-one with sub-detection sequences X1 to Xn. After being transmitted via optical fiber link Z, sub-optical signals F1 to Fn become sub-optical signals G1 to Gn. Sub-optical signals G1 to Gn are the multiple received sub-optical signals included in the second optical signal, and sub-optical signals G1 to Gn correspond one-to-one with sub-optical signals F1 to Fn. Sub-optical signal G1 includes sub-optical signal F1 and sub-reflected optical signal R1, sub-optical signal G2 includes sub-optical signal F2 and sub-reflected optical signal R2, and so on. Sub-optical signal Gn includes sub-optical signal Fn and sub-reflected optical signal Rn. The reflected optical signal R includes sub-reflected optical signals R1 to Rn. Figure 14As shown, optical transmitting device 210 includes optical transmitters 1 to n, optical receiving device 220 includes optical receivers 1 to n, and optical fiber link Z includes parallel optical fibers 1 to n. Optical transmitters 1 to n are connected one-to-one with optical fibers 1 to n, and optical receivers 1 to n are also connected one-to-one with optical fibers 1 to n. Optical transmitters 1 to n generate sub-optical signals F1 to Fn, each sub-optical signal F1 to Fn carrying a sub-detection sequence X1 to Xn (that is, sub-optical signal F1 carries sub-detection sequence X1, sub-optical signal F2 carries sub-detection sequence X2, and so on, sub-optical signal Fn carries sub-detection sequence Xn). Optical transmitters 1 to n transmit sub-optical signals F1 to Fn to optical receiving device 220 through optical fibers 1 to n. Optical receivers 1 to n receive sub-optical signals G1 to Gn through optical fibers 1 to n.

[0236] The third scenario (corresponding to the third scenario in S301): The multiplexing method is time-division multiplexing. The first optical signal carries a first sub-detection sequence in the first time period, and a second sub-detection sequence in the second time period. These multiple sub-detection sequences include both the first and second sub-detection sequences. The optical transmitting device sends the first optical signal carrying the first sub-detection sequence to the optical receiving device via fiber optic link Z in the first time period. The optical transmitting device also sends the first optical signal carrying the second sub-detection sequence to the optical receiving device via fiber optic link Z in the second time period. The optical receiving device receives the second optical signal carrying the first sub-detection sequence via fiber optic link Z in the first time period, and the same applies to the second optical signal carrying the second sub-detection sequence in the second time period. For example, these multiple sub-detection sequences correspond one-to-one with multiple time periods. The first optical signal carries the corresponding sub-detection sequence in each time period, and the optical transmitting device sends the first optical signal carrying the corresponding sub-detection sequence to the optical receiving device via fiber optic link Z in each time period; the optical receiving device receives the second optical signal carrying the corresponding sub-detection sequence via fiber optic link Z in each time period.

[0237] As an example, the multiple time periods are time periods T1 to Tn, and the multiple sub-detection sequences included in the detection sequence X are sub-detection sequences X1 to Xn, with each sub-detection sequence X1 to Xn corresponding one-to-one with the time periods T1 to Tn. For example... Figure 19As shown, the optical transmitting device 210 includes an optical transmitter, and the optical receiving device 220 includes an optical receiver. Both the optical transmitter and receiver are connected to an optical fiber link Z. During time period T1, the optical transmitter generates a first optical signal carrying a sub-detection sequence X1 and transmits this first optical signal to the optical receiving device 220 via the optical fiber link Z. During time period T1, the optical receiver receives a second optical signal carrying the sub-detection sequence X1 via the optical fiber link Z. During time period T2, the optical transmitter generates a first optical signal carrying a sub-detection sequence X2 and transmits this first optical signal to the optical receiving device 220 via the optical fiber link Z. During time period T2, the optical receiver receives the second optical signal carrying the sub-detection sequence X2 via the optical fiber link Z. This process continues. During time period Tn, the optical transmitter generates a first optical signal carrying the sub-detection sequence Xn and sends the first optical signal carrying the sub-detection sequence Xn to the optical receiving device 220 through the optical fiber link Z during time period Tn; during time period Tn, the optical receiver receives a second optical signal carrying the sub-detection sequence Xn through the optical fiber link Z.

[0238] S304. The optical receiving device demodulates the second optical signal to obtain the detection sequence X.

[0239] In a specific embodiment, the detection sequence X includes multiple sub-detection sequences, and the optical receiving device demodulates the second optical signal to obtain these multiple sub-detection sequences. As mentioned earlier, these multiple sub-detection sequences are carried in the first optical signal in a multiplexed manner, and therefore, they are carried in the second optical signal in a multiplexed manner. The multiplexing method includes any one of wavelength division multiplexing, parallel fiber multiplexing, or time division multiplexing. Depending on the multiplexing method, the first optical signal is different, the second optical signal is different, and the demodulation process of the second optical signal by the optical receiving device is different. The implementation process of S304 (i.e., the demodulation of the second optical signal by the optical receiving device) is described below in three cases.

[0240] The first scenario (corresponding to the first scenario in S301 to S303): The multiplexing method is wavelength division multiplexing (WDM). The first optical signal includes multiple sub-optical signals (i.e., transmit sub-optical signals), each corresponding to a sub-detection sequence. Each transmit sub-optical signal carries the corresponding sub-detection sequence. The second optical signal includes multiple receive sub-optical signals, each corresponding to a transmit sub-optical signal. Each receive sub-optical signal includes the corresponding transmit sub-optical signal and a sub-reflected optical signal generated by the reflection of the corresponding transmit sub-optical signal in the optical fiber link Z. The optical fiber link Z includes a first optical fiber. The optical transmitting device transmits the first optical signal to the optical receiving device through the first optical fiber. The optical receiving device receives the second optical signal through the first optical fiber. The optical receiving device demultiplexes the second optical signal to obtain the multiple receive sub-optical signals. The optical receiving device demodulates each receive sub-optical signal to obtain the sub-detection sequence carried by each receive sub-optical signal. For example, an optical receiving device includes an optical demultiplexer that demultiplexes a second optical signal to obtain the plurality of received sub-optical signals.

[0241] As an example, the first optical signal includes the aforementioned multiple transmitted sub-optical signals F1 to Fn, and the detection sequence X includes the aforementioned multiple sub-detection sequences X1 to Xn. Sub-optical signals F1 to Fn correspond one-to-one with sub-detection sequences X1 to Xn. The first optical signal is obtained by multiplexing sub-optical signals F1 to Fn using an optical transmitting device. After transmission via fiber optic link Z, sub-optical signals F1 to Fn become sub-optical signals G1 to Gn. Sub-optical signals G1 to Gn are the multiple received sub-optical signals included in the second optical signal, and they correspond one-to-one with sub-optical signals F1 to Fn. Sub-optical signal G1 includes sub-optical signal F1 and sub-reflected optical signal R1; sub-optical signal G2 includes sub-optical signal F2 and sub-reflected optical signal R2, and so on. Sub-optical signal Gn includes sub-optical signal Fn and sub-reflected optical signal Rn. The reflected optical signal R includes sub-reflected optical signals R1 to Rn. An optical receiving device receives a second optical signal through a first optical fiber. The optical receiving device demultiplexes the second optical signal to obtain sub-optical signals G1 to Gn. The optical receiving device then demodulates each of the sub-optical signals G1 to Gn to obtain sub-detection sequences X1 to Xn. That is, the optical receiving device demodulates sub-optical signal G1 to obtain sub-detection sequence X1, demodulates sub-optical signal G2 to obtain sub-detection sequence X2, and so on, demodulating sub-optical signal Gn to obtain sub-detection sequence Xn. For example... Figure 13As shown, the optical transmitting device 210 includes optical transmitters 1-n and an optical multiplexer, and the optical receiving device 220 includes an optical demultiplexer, optical receivers 1-n, and a demodulation unit. The optical fiber link Z includes a first optical fiber. The optical multiplexer is connected to the optical transmitters 1-n respectively, and the optical multiplexer is connected to the first optical fiber. The optical demultiplexer is connected to the optical receivers 1-n respectively, and the optical demultiplexer is connected to the first optical fiber. The demodulation unit is connected to the optical receivers 1-n respectively. The optical transmitters 1-n generate sub-optical signals F1-Fn one-to-one, and each sub-optical signal F1-Fn carries a sub-detection sequence X1-Xn. The optical multiplexer multiplexes the sub-optical signals F1-Fn to obtain a first optical signal, and the optical multiplexer transmits the first optical signal to the optical receiving device 220 through the first optical fiber. After being transmitted through the first optical fiber, the first optical signal becomes a second optical signal, and the optical demultiplexer receives the second optical signal through the first optical fiber. An optical demultiplexer demultiplexes the second optical signal to obtain sub-optical signals G1 to Gn, which correspond one-to-one with optical receivers 1 to n. The optical demultiplexer transmits the sub-optical signals G1 to Gn to each of the optical receivers 1 to n. The demodulation unit demodulates the sub-optical signals G1 to Gn to obtain the sub-detection sequences X1 to Xn. For example, optical receivers 1 to n convert the sub-optical signals G1 to Gn into electrical signals, and then transmit the corresponding electrical signals to the demodulation unit. The demodulation unit demodulates these electrical signals to obtain the sub-detection sequences X1 to Xn.

[0242] The second scenario (corresponding to the second scenario in S301 to S303): The multiplexing method is parallel fiber multiplexing. The first optical signal includes multiple sub-optical signals (i.e., transmit sub-optical signals), each corresponding to a sub-detection sequence. Each transmit sub-optical signal carries the corresponding sub-detection sequence. The second optical signal includes multiple receive sub-optical signals, each corresponding to a transmit sub-optical signal. Each receive sub-optical signal includes the corresponding transmit sub-optical signal and a sub-reflected optical signal generated by the reflection of the corresponding transmit sub-optical signal in the fiber optic link Z. The fiber optic link Z includes multiple parallel optical fibers, each corresponding to a transmit sub-optical signal. The optical transmitting device transmits the transmit sub-optical signals to the optical receiving device through these optical fibers, and the optical receiving device receives the receive sub-optical signals through these optical fibers. The optical receiving device demodulates each receive sub-optical signal to obtain the sub-detection sequence carried by each receive sub-optical signal.

[0243] As an example, the first optical signal includes the aforementioned multiple transmitted sub-optical signals F1 to Fn, and the detection sequence X includes the aforementioned multiple sub-detection sequences X1 to Xn. Sub-optical signals F1 to Fn correspond one-to-one with sub-detection sequences X1 to Xn. After being transmitted via fiber optic link Z, sub-optical signals F1 to Fn become sub-optical signals G1 to Gn. Sub-optical signals G1 to Gn are the multiple received sub-optical signals included in the second optical signal, and they correspond one-to-one with sub-optical signals F1 to Fn. Sub-optical signal G1 includes sub-optical signal F1 and sub-reflected optical signal R1; sub-optical signal G2 includes sub-optical signal F2 and sub-reflected optical signal R2, and so on. Sub-optical signal Gn includes sub-optical signal Fn and sub-reflected optical signal Rn. The reflected optical signal R includes sub-reflected optical signals R1 to Rn. Figure 14 As shown, the optical transmitting device 210 includes optical transmitters 1 to n, the optical receiving device 220 includes optical receivers 1 to n and a demodulation unit, and the optical fiber link Z includes optical fibers 1 to n. Optical transmitters 1 to n are connected one-to-one with optical fibers 1 to n, optical receivers 1 to n are connected one-to-one with optical fibers 1 to n, and the demodulation unit is connected to each of the optical receivers 1 to n. Optical transmitters 1 to n generate sub-optical signals F1 to Fn, each sub-optical signal F1 to Fn carrying a sub-detection sequence X1 to Xn. Optical transmitters 1 to n transmit the sub-optical signals F1 to Fn to the optical receiving device 220 through optical fibers 1 to n. Optical receivers 1 to n receive the sub-optical signals G1 to Gn through optical fibers 1 to n. The demodulation unit demodulates the sub-optical signals G1 to Gn to obtain the sub-detection sequences X1 to Xn. That is, the demodulation unit demodulates the sub-optical signal G1 to obtain the sub-detection sequence X1, the demodulation unit demodulates the sub-optical signal G2 to obtain the sub-detection sequence X2, and so on, the demodulation unit demodulates the sub-optical signal Gn to obtain the sub-detection sequence Xn. For example, optical receivers 1 to n convert the sub-optical signals G1 to Gn into electrical signals in a one-to-one correspondence, and optical receivers 1 to n send the electrical signals corresponding to the sub-optical signals G1 to Gn to the demodulation unit, and the demodulation unit demodulates the electrical signals corresponding to the sub-optical signals G1 to Gn one by one to obtain the sub-detection sequences X1 to Xn.

[0244] In optional embodiments, in the first and second cases described above, the plurality of sub-detection sequences include a first sub-detection sequence, and the plurality of transmitted sub-optical signals include a first sub-optical signal, with the first sub-optical signal corresponding to the first sub-detection sequence. The first sub-optical signal carries a plurality of first sub-detection sequences, which are periodically distributed within the first sub-optical signal. There are boundary markers between adjacent first sub-detection sequences among the plurality of first sub-detection sequences; or, adjacent first sub-detection sequences among the plurality of first sub-detection sequences are continuous. After transmission via optical fiber link Z, the first sub-optical signal becomes a third sub-optical signal, which includes the first sub-optical signal and a first sub-reflected optical signal. The second optical signal includes the third sub-optical signal (the third sub-optical signal is a received sub-optical signal included in the second optical signal), and the reflected optical signal R includes the first sub-reflected optical signal. The demodulation process of the received sub-optical signal by the optical receiving device is described below using the third sub-optical signal as an example.

[0245] In one embodiment, a first sub-optical signal carries a plurality of first detection sub-sequences, which are periodically distributed and have boundary markers between adjacent first sub-detection sequences. Correspondingly, a third sub-optical signal carries the same plurality of first detection sub-sequences, which are also periodically distributed and have boundary markers between adjacent first sub-detection sequences. The optical receiving device determines the first sub-detection sequence carried by the third sub-optical signal based on the boundary markers carried by the third sub-optical signal.

[0246] In a specific implementation of this embodiment, the optical receiving device searches for boundary markers in the third sub-optical signal. The optical receiving device determines (i.e., identifies) the start and / or end positions of the first sub-detection sequence carried by the third sub-optical signal based on the boundary markers found in the third sub-optical signal. The optical receiving device determines the first sub-detection sequence carried by the third sub-optical signal based on the identified start and / or end positions. In one example, the optical receiving device identifies the start and end positions of the first sub-detection sequence carried by the third sub-optical signal based on the boundary markers carried by the third sub-optical signal, and the optical receiving device defines the portion between the identified start and end positions as a first sub-detection sequence. In another example, the optical receiving device identifies the start position of the first sub-detection sequence carried by the third sub-optical signal based on the boundary markers carried by the third sub-optical signal, and the optical receiving device defines the portion between adjacent identified start positions as a first sub-detection sequence. In yet another example, the optical receiving device identifies the end position of the first sub-detection sequence carried by the third sub-optical signal based on the boundary markers carried by the third sub-optical signal, and the optical receiving device defines the portion between adjacent identified end positions as a first sub-detection sequence. Since the multiple first sub-detection sequences are periodically distributed in the third sub-optical signal, after the optical receiving device determines one of the first sub-detection sequences carried by the third sub-optical signal based on the boundary marker carried by the third sub-optical signal, the optical receiving device can determine other first sub-detection sequences carried by the third sub-optical signal based on the distribution period of the multiple first sub-detection sequences. This application embodiment does not limit this.

[0247] In another embodiment, the first sub-optical signal carries multiple first detection sub-sequences, which are periodically distributed, adjacent first sub-detection sequences are continuous, and there are no boundary markers between adjacent first sub-detection sequences. Correspondingly, the third sub-optical signal carries the same multiple first detection sub-sequences, which are also periodically distributed, adjacent first sub-detection sequences are continuous, and there are no boundary markers between adjacent first sub-detection sequences. The optical receiving device determines the first sub-detection sequence carried by the third sub-optical signal based on the characteristics of the first sub-detection sequences. The characteristics of the first sub-detection sequences may be distribution characteristics or correlation characteristics (e.g., autocorrelation characteristics), etc.

[0248] In another specific implementation of this embodiment, the optical receiving device extracts a sequence from the third sub-optical signal (e.g., randomly extracts a sequence) based on the length of a first sub-detection sequence known to the optical receiving device. For ease of description, the sequence extracted by the optical receiving device from the third sub-optical signal is referred to as the test sequence, and the length of the test sequence is equal to the length of the first sub-detection sequence known to the optical receiving device. The optical receiving device verifies whether the test sequence is a first sub-detection sequence based on the first sub-detection sequence known to the optical receiving device. If the verification determines that the test sequence is a first sub-detection sequence, the optical receiving device determines that a first sub-detection sequence has been found in the third sub-optical signal, and the optical receiving device determines other first sub-detection sequences carried by the third sub-optical signal based on the distribution period of the plurality of first sub-detection sequences. If the verification determines that the test sequence is not a first sub-detection sequence, the optical receiving device re-extracts the test sequence from the third sub-optical signal and verifies whether the re-extracted test sequence is a first sub-detection sequence, until a first sub-detection sequence is found in the third sub-optical signal. In one example, the optical receiving device performs a correlation calculation between the sequence to be tested and a first sub-detection sequence known to the optical receiving device; the optical receiving device determines whether the sequence to be tested is the first sub-detection sequence based on the correlation calculation result. In a specific embodiment, the optical receiving device performs a correlation calculation between the sequence to be tested and the first sub-detection sequence known to the optical receiving device to obtain a cross-correlation curve between the sequence to be tested and the first sub-detection sequence known to the optical receiving device; the optical receiving device compares the cross-correlation curve with the autocorrelation curve of the first sub-detection sequence known to the optical receiving device to determine whether the cross-correlation curve and the autocorrelation curve match; if the comparison determines that the cross-correlation curve and the autocorrelation curve match, the optical receiving device determines that the sequence to be tested is the first sub-detection sequence; if the comparison determines that the cross-correlation curve and the autocorrelation curve do not match, the optical receiving device determines that the sequence to be tested is not the first sub-detection sequence. In another example, the optical receiving device compares the sequence to be tested with a first sub-detection sequence known to the optical receiving device to determine whether the sequence to be tested matches the first sub-detection sequence known to the optical receiving device; if the comparison determines that the sequence to be tested matches the first sub-detection sequence known to the optical receiving device, the optical receiving device determines that the sequence to be tested is the first sub-detection sequence; if the comparison determines that the sequence to be tested does not match the first sub-detection sequence known to the optical receiving device, the optical receiving device determines that the sequence to be tested is not the first sub-detection sequence.

[0249] The term "matching" as described above includes, but is not limited to, being substantially the same or completely identical. "Substantially the same" means essentially identical but with minor differences. For ease of description, the cross-correlation curve between the sequence to be tested and the first known sub-detection sequence of the optical receiving device is referred to as the cross-correlation curve Q1, and the first known sub-detection sequence of the optical receiving device is referred to as the autocorrelation curve Q2. The fact that the cross-correlation curve Q1 and the autocorrelation curve Q2 are substantially the same includes: the number of time-shifted symbols at each position point on the cross-correlation curve Q1 is the same as the number of time-shifted symbols at the corresponding position point on the autocorrelation curve Q2, and the correlation value at each position point on the cross-correlation curve Q1 is substantially the same as the correlation value at the corresponding position point on the autocorrelation curve Q2 (e.g., the correlation values ​​are equal or the difference in correlation values ​​is less than a threshold). For example, the cross-correlation curve Q1 and the autocorrelation curve Q2 each include position points -w to w. The correlation value of position point -w on the cross-correlation curve Q1 is approximately the same as the correlation value of position point -w on the autocorrelation curve Q2. The correlation value of position point -w+1 on the cross-correlation curve Q1 is approximately the same as the correlation value of position point -w+1 on the autocorrelation curve Q2. The correlation value of position point -w+2 on the cross-correlation curve Q1 is approximately the same as the correlation value of position point -w+2 on the autocorrelation curve Q2, and so on. Matching the sequence to be tested with the first sub-detection sequence known by the optical receiving device includes: multiple symbols of the sequence to be tested correspond one-to-one with multiple symbols of the first sub-detection sequence known by the optical receiving device; the amplitude of the symbol of the sequence to be tested is approximately the same as the amplitude of the corresponding symbol of the first sub-detection sequence known by the optical receiving device (e.g., the amplitudes are equal or the difference in amplitude is less than a threshold). For example, if the sequence to be tested is -1,-1,1.2,-1,-1,-1,-1,1,-1,-1.3,-1,1,-1,1,1,1,-1, and the first sub-detection sequence known by the optical receiving device is -1,-1,1,-1,-1,-1,-1,1,-1,-1,1,-1,1,1,-1,1,1,-1, then the sequence to be tested matches the first sub-detection sequence known by the optical receiving device.

[0250] It should be noted that the first sub-detection sequence known to the optical receiving device is a first sub-detection sequence that the optical receiving device obtains in any possible way. For example, the first sub-detection sequence known to the optical receiving device is a first sub-detection sequence pre-negotiated between the optical transmitting device and the optical receiving device, or a first sub-detection sequence pre-configured in the optical receiving device. In specific embodiments, the optical transmitting device and the optical receiving device pre-negotiate detection sequence X and each sub-detection sequence included in detection sequence X, or the optical receiving device pre-configures detection sequence X and each sub-detection sequence included in detection sequence X. In some embodiments, the optical transmitting device and the optical receiving device may pre-negotiate the length of the first sub-detection sequence (e.g., negotiate the length of each sub-detection sequence included in detection sequence X), or the optical receiving device pre-configures the length of the first sub-detection sequence (e.g., pre-configure the length of each sub-detection sequence included in detection sequence X). For example, the length of the first sub-detection sequence is referred to as the first length. The optical receiving device extracts the sequence to be tested from the third sub-optical signal according to a first length, the length of which is equal to the first length; the optical receiving device performs a hard decision on the sequence to be tested to obtain a hard decision sequence; the optical receiving device uses the hard decision sequence as the first sub-detection sequence known to the optical receiving device, and then verifies whether the sequence to be tested is the first sub-detection sequence based on the first sub-detection sequence known to the optical receiving device (i.e., the hard decision sequence). This application embodiment does not limit this.

[0251] In an optional embodiment, the optical receiving device converts the third sub-optical signal into an electrical signal, and demodulates the electrical signal to obtain a first sub-detection sequence. For example, the optical receiving device performs photoelectric conversion on the third sub-optical signal to obtain an analog electrical signal; the optical receiving device converts the analog electrical signal into a digital electrical signal; the optical receiving device determines the first sub-detection sequence based on the digital electrical signal. In one embodiment, the third sub-optical signal carries multiple periodically distributed first sub-detection sequences, with boundary markers between adjacent first sub-detection sequences; therefore, the digital electrical signal carries multiple periodically distributed first sub-detection sequences, with boundary markers between adjacent first sub-detection sequences. The optical receiving device searches for boundary markers in the digital electrical signal, identifies the start and / or end positions of the first sub-detection sequences carried by the digital electrical signal based on the boundary markers found in the digital electrical signal, and determines the first sub-detection sequence carried by the digital electrical signal based on the start and / or end positions identified from the digital electrical signal. In another embodiment, the third sub-optical signal carries a plurality of periodically distributed first sub-detection sequences, with adjacent first sub-detection sequences being consecutive. Therefore, the digital electrical signal carries a plurality of periodically distributed first sub-detection sequences, with adjacent first sub-detection sequences being consecutive. The optical receiving device determines the first sub-detection sequences from the digital electrical signal based on the characteristics of the first sub-detection sequences.

[0252] Since digital electrical signals typically contain noise, optical receiving devices can perform noise reduction and equalization processing on them to reduce the impact of noise. The optical receiving device then determines the first sub-detection sequence from the noise-reduced and equalized digital electrical signal, thus avoiding the interference of noise in determining the first sub-detection sequence. The process by which the optical receiving device determines (or searches for, identifies) the first sub-detection sequence from the digital electrical signal can be called a synchronization process. For example, such as... Figure 13 and Figure 14 As shown, the optical receiving device 220 includes optical receivers 1 to n and a demodulation unit, which is connected to each of the optical receivers 1 to n. Each of the optical receivers 1 to n includes a first optical receiver (for example, any one of the optical receivers 1 to n). The first optical receiver is used to perform photoelectric conversion on the third sub-optical signal to obtain an analog electrical signal; the demodulation unit is used to: convert the analog electrical signal into a digital electrical signal; perform noise reduction and equalization processing on the digital electrical signal, and determine (or search for, identify) a first sub-detection sequence from the digital electrical signal. In a specific example, the demodulation unit includes a sampling quantization subunit, a synchronization subunit, and a noise reduction subunit. The sampling quantization subunit is used to convert the analog electrical signal into a digital electrical signal; the synchronization subunit is used to determine (or search for, identify) the first sub-detection sequence from the digital electrical signal; and the noise reduction subunit is used to perform noise reduction and equalization processing on the digital electrical signal.

[0253] In an optional embodiment, the first sub-optical signal further carries a first data signal, and the first sub-detection sequence is modulated on the first data signal (i.e., the first sub-detection sequence and the first data signal are carried in the same field); correspondingly, the third sub-optical signal further carries the first data signal, and the first sub-detection sequence is modulated on the first data signal. Demodulation of the third sub-optical signal by the optical receiving device further includes: filtering the third sub-optical signal to obtain a detection signal, which carries the first sub-detection sequence. For example, the detection signal carries multiple periodically distributed first sub-detection sequences. If the third sub-optical signal also carries a boundary marker, the detection signal also carries a boundary marker. The detection signal includes noise, and a portion of the noise in the detection signal may be the first data signal. In one embodiment, the optical receiving device performs photoelectric conversion on the third sub-optical signal to obtain an analog electrical signal; the optical receiving device converts the analog electrical signal into a digital electrical signal; the optical receiving device filters the digital electrical signal to obtain a filtered digital electrical signal, which is the detection signal; the optical receiving device determines the first sub-detection sequence based on the filtered digital electrical signal. In another embodiment, the optical receiving device performs photoelectric conversion on the third sub-optical signal to obtain an analog electrical signal; the optical receiving device filters the analog electrical signal to obtain a filtered analog electrical signal; the optical receiving device converts the filtered analog electrical signal into a digital electrical signal, which is the detection signal; the optical receiving device determines the first sub-detection sequence based on the digital electrical signal. That is, the optical receiving device can filter either the analog electrical signal or the digital electrical signal. The optical receiving device uses an analog filter to filter the analog electrical signal and a digital filter to filter the digital electrical signal. For example, the first sub-detection sequence is modulated onto the first data signal, the modulation depth of the first sub-detection sequence is less than the modulation depth of the first data signal, and the baud rate of the first sub-detection sequence is less than the baud rate of the first data signal. Both the analog filter and the digital filter are low-pass filters.

[0254] In this embodiment, the third sub-optical signal can be any one of the multiple received sub-optical signals included in the second optical signal. The demodulation process of each of the multiple received sub-optical signals by the optical receiving device can refer to the demodulation process of the third sub-optical signal by the optical receiving device, and will not be elaborated here. For example, the multiple received sub-optical signals may also include a fourth sub-optical signal carrying a second sub-detection sequence. The optical receiving device further demodulates the fourth sub-optical signal to obtain the second sub-detection sequence.

[0255] The third scenario (corresponding to the third scenario in S301 to S303): The multiplexing method is time-division multiplexing. The first optical signal carries a first sub-detection sequence in the first time period, and a second sub-detection sequence in the second time period. These multiple sub-detection sequences include both the first and second sub-detection sequences. Correspondingly, the second optical signal carries the first sub-detection sequence in the first time period and the second sub-detection sequence in the second time period. The optical transmitting device sends the first optical signal carrying the first sub-detection sequence to the optical receiving device via fiber optic link Z in the first time period. The optical transmitting device sends the first optical signal carrying the second sub-detection sequence to the optical receiving device via fiber optic link Z in the second time period. The optical receiving device receives the second optical signal carrying the first sub-detection sequence via fiber optic link Z in the first time period and demodulates the second optical signal to obtain the first sub-detection sequence. The optical receiving device receives the second optical signal carrying the second sub-detection sequence via fiber optic link Z in the second time period and demodulates the second optical signal to obtain the second sub-detection sequence. For example, the multiple sub-detection sequences correspond one-to-one with multiple time periods. The optical transmitting device sends a first optical signal carrying the corresponding sub-detection sequence to the optical receiving device through the optical fiber link Z in each of the multiple time periods. The optical receiving device receives a second optical signal carrying the corresponding sub-detection sequence through the optical fiber link Z in each of the multiple time periods, and demodulates the second optical signal to obtain the corresponding sub-detection sequence.

[0256] In an optional embodiment, in this third case, the first optical signal carries a plurality of first sub-detection sequences in a first time period, the plurality of first sub-detection sequences being periodically distributed in the first optical signal; there are boundary markers between adjacent first sub-detection sequences among the plurality of first sub-detection sequences; or, adjacent first sub-detection sequences among the plurality of first sub-detection sequences are continuous. Correspondingly, the second optical signal carries a plurality of first sub-detection sequences in the first time period, the plurality of first sub-detection sequences being periodically distributed in the second optical signal; there are boundary markers between adjacent first sub-detection sequences among the plurality of first sub-detection sequences; or, adjacent first sub-detection sequences among the plurality of first sub-detection sequences are continuous.

[0257] In one embodiment, the second optical signal carries a plurality of first sub-detection sequences in a first time period. These plurality of first sub-detection sequences are periodically distributed in the second optical signal, and there are boundary markers between adjacent first sub-detection sequences. The optical receiving device determines the first sub-detection sequences carried by the second optical signal based on the boundary markers carried by the second optical signal. For a detailed implementation, refer to the above-described implementation process of the optical receiving device determining the first sub-detection sequences carried by the third sub-optical signal based on the boundary markers carried by the third sub-optical signal.

[0258] In another embodiment, the second optical signal carries a plurality of first sub-detection sequences in a first time period. These plurality of first sub-detection sequences are periodically distributed in the second optical signal, and adjacent first sub-detection sequences are consecutive. The optical receiving device determines the first sub-detection sequence carried by the second optical signal based on the characteristics of the first sub-detection sequences. For a detailed implementation process, refer to the above-described implementation process of the optical receiving device determining the first sub-detection sequence carried by the third sub-optical signal based on the characteristics of the first sub-detection sequence.

[0259] In an optional embodiment, the optical receiving device converts the second optical signal received in the first time period into an electrical signal, and demodulates the electrical signal to obtain a first sub-detection sequence. For example, the optical receiving device performs photoelectric conversion on the second optical signal to obtain an analog electrical signal; the optical receiving device converts the analog electrical signal into a digital electrical signal; and the optical receiving device determines the first sub-detection sequence based on the digital electrical signal. Optionally, the optical receiving device performs noise reduction processing, equalization processing, etc., on the digital electrical signal to reduce the impact of noise on the digital electrical signal. The optical receiving device determines the first sub-detection sequence from the digital electrical signal after noise reduction and equalization processing. For example... Figure 19 As shown, the optical receiving device 220 includes an optical receiver and a demodulation unit connected to the optical receiver. The optical receiver performs photoelectric conversion on the second optical signal to obtain an analog electrical signal; the demodulation unit performs: conversion of the analog electrical signal into a digital electrical signal; noise reduction processing, equalization processing, etc., on the digital electrical signal; and determines a first sub-detection sequence from the digital electrical signal. For example, the demodulation unit includes a sampling quantization subunit, a synchronization subunit, and a noise reduction subunit. The sampling quantization subunit converts the analog electrical signal into a digital electrical signal; the synchronization subunit determines the first sub-detection sequence from the digital electrical signal; and the noise reduction subunit performs noise reduction processing, equalization processing, etc., on the digital electrical signal.

[0260] In an optional embodiment, the first optical signal also carries a data signal. For example, the first sub-optical signal carries a first sub-detection sequence and a first data signal in a first time period, with the first sub-detection sequence modulated on the first data signal (i.e., the first sub-detection sequence and the first data signal are carried in the same field). Correspondingly, the second optical signal also carries the first sub-detection sequence and the first data signal in the first time period, with the first sub-detection sequence modulated on the first data signal. Demodulating the second optical signal received by the optical receiving device in the first time period further includes: filtering the second optical signal to obtain a detection signal, which carries the first sub-detection sequence. For example, the detection signal carries a plurality of periodically distributed first sub-detection sequences. If the second optical signal also carries a boundary marker, the detection signal also carries a boundary marker. The detection signal includes noise, and a portion of the noise in the detection signal may be the first data signal. In one embodiment, the optical receiving device performs photoelectric conversion on the second optical signal to obtain an analog electrical signal; the optical receiving device converts the analog electrical signal into a digital electrical signal; the optical receiving device filters the digital electrical signal to obtain a filtered digital electrical signal, which is the detection signal; the optical receiving device determines a first sub-detection sequence based on the filtered digital electrical signal. In another embodiment, the optical receiving device performs photoelectric conversion on the second optical signal to obtain an analog electrical signal; the optical receiving device filters the analog electrical signal to obtain a filtered analog electrical signal; the optical receiving device converts the filtered analog electrical signal into a digital electrical signal, which is the detection signal; the optical receiving device determines a first sub-detection sequence based on the digital electrical signal. The optical receiving device uses an analog filter to filter the analog electrical signal and a digital filter to filter the digital electrical signal. For example, the first sub-detection sequence is modulated onto a first data signal, the modulation depth of the first sub-detection sequence is less than the modulation depth of the first data signal, and the baud rate of the first sub-detection sequence is less than the baud rate of the first data signal; both the analog filter and the digital filter are low-pass filters.

[0261] The above description uses the demodulation of a second optical signal received in a first time period by an optical receiving device as an example. The demodulation process of a second optical signal received in any time period by an optical receiving device can be referred to the above description and will not be repeated here. It should be noted that the length of the first time period is the same for both the optical transmitting and receiving devices, but the position of the first time period on the time axis may differ. For example, shifting the position of the first time period for the optical transmitting device along the positive direction of the time axis by a certain duration yields the first time period for the optical receiving device; this certain duration is the transmission duration of the first optical signal in the fiber optic link Z. The meanings of other time periods are similar.

[0262] S305. The optical receiving device determines the transmission performance of the optical fiber link Z based on the demodulated detection sequence X.

[0263] The detection sequence X includes multiple sub-detection sequences (e.g., sub-detection sequences X1 to Xn). According to S305, the optical receiving device demodulates the second optical signal to obtain these multiple sub-detection sequences. That is, the optical receiving device demodulates these multiple sub-detection sequences from the second optical signal. Demodulating these multiple sub-detection sequences from the second optical signal is equivalent to the optical receiving device demodulating the detection sequence X from the second optical signal.

[0264] In an optional embodiment, the optical receiving device acquires the correlation curve of each sub-detection sequence demodulated from the second optical signal; the optical receiving device determines the correlation curve corresponding to the detection sequence X demodulated from the second optical signal based on the correlation curves of the plurality of sub-detection sequences (e.g., sub-detection sequences X1 to Xn) demodulated from the second optical signal; the optical receiving device determines the transmission performance of the optical fiber link Z based on the correlation curve corresponding to the detection sequence X demodulated from the second optical signal. The correlation curve can be an autocorrelation curve or a cross-correlation curve. The cross-correlation curve of each sub-detection sequence demodulated from the second optical signal is determined based on each sub-detection sequence demodulated from the second optical signal and each sub-detection sequence known to the optical receiving device. The correlation curve corresponding to the detection sequence X demodulated from the second optical signal can be a superposition curve of the correlation curves of the plurality of sub-detection sequences demodulated from the second optical signal. For example, the autocorrelation curve corresponding to the detection sequence X demodulated from the second optical signal is a superposition curve of the autocorrelation curves of the plurality of sub-detection sequences demodulated from the second optical signal. The cross-correlation curve corresponding to the detection sequence X demodulated from the second optical signal is a superposition curve of the cross-correlation curves of the plurality of sub-detection sequences demodulated from the second optical signal. In some embodiments, the cross-correlation curve of each sub-detection sequence demodulated from the second optical signal can also be considered as the autocorrelation curve of each sub-detection sequence demodulated from the second optical signal, and the cross-correlation curve corresponding to the detection sequence X demodulated from the second optical signal can also be considered as the autocorrelation curve corresponding to the detection sequence X demodulated from the second optical signal.

[0265] In an optional embodiment, the autocorrelation curve corresponding to the detection sequence X carried by the first optical signal satisfies a preset condition. The optical receiving device determines the transmission performance of the optical fiber link Z based on the correlation curve (autocorrelation curve or cross-correlation curve) corresponding to the detection sequence X demodulated from the second optical signal and the preset condition. In a specific embodiment, the optical receiving device determines whether the correlation curve corresponding to the detection sequence X demodulated from the second optical signal satisfies the preset condition. If the correlation curve satisfies the preset condition, the optical receiving device determines that the optical fiber link Z is fault-free. If the correlation curve does not satisfy the preset condition, the optical receiving device determines that the optical fiber link Z is faulty.

[0266] In an optional embodiment, the autocorrelation curve corresponding to the detection sequence X carried by the first optical signal (i.e., the detection sequence X modulated on the first optical signal by the optical transmitting device) satisfies a preset condition including that the autocorrelation curve corresponding to the detection sequence X has a characteristic peak. The optical receiving device determines the transmission performance of the optical fiber link Z based on the characteristic peak of the correlation curve corresponding to the detection sequence X demodulated from the second optical signal. In a specific embodiment, the optical receiving device determines whether there is a fault in the optical fiber link Z based on the characteristic peak of the correlation curve corresponding to the detection sequence X demodulated from the second optical signal. For example, the autocorrelation curve corresponding to the detection sequence X carried by the first optical signal satisfies a preset condition including: the autocorrelation curve corresponding to the detection sequence X has only one characteristic peak. The optical receiving device determines the number of characteristic peaks of the correlation curve corresponding to the detection sequence X demodulated from the second optical signal. If the correlation curve has only one characteristic peak, the optical receiving device determines that the optical fiber link Z is fault-free. If the correlation curve has multiple characteristic peaks, the optical receiving device determines that the optical fiber link Z is faulty.

[0267] In an optional embodiment, when the correlation curve corresponding to the detection sequence X demodulated from the second optical signal has multiple characteristic peaks, the optical receiving device determines the fault point on the optical fiber link Z based on the main peak and the secondary peaks among the multiple characteristic peaks. The multiple characteristic peaks include one main peak and at least one secondary peak, the peak value of which is smaller than the peak value of the main peak. Each of the at least one secondary peak corresponds to two reflection points on the optical fiber link Z, and at least one of these two reflection points is the fault point. Furthermore, the partial reflection points corresponding to different secondary peaks can be the same or different. For example, the at least one secondary peak includes secondary peak 1 and secondary peak 2, where secondary peak 1 corresponds to reflection point 1 and reflection point 2, and secondary peak 2 corresponds to reflection point 1 and reflection point 3; that is, the partial reflection points corresponding to secondary peak 1 and secondary peak 2 are the same.

[0268] In a specific embodiment, the horizontal axis of the correlation curve corresponding to the detection sequence X demodulated from the second optical signal represents the number of time-shifted symbols. When the correlation curve includes a main peak and at least one secondary peak, for each of the at least one secondary peak: the optical receiving device determines the difference between the number of time-shifted symbols corresponding to the secondary peak and the number of time-shifted symbols corresponding to the main peak (for ease of description, this difference is referred to as the time-shifted symbol difference corresponding to the secondary peak); the optical receiving device determines the transmission duration of the reflected optical signal between the two reflection points corresponding to the secondary peak based on the time-shifted symbol difference corresponding to the secondary peak and the baud rate of the detection sequence X carried by the first optical signal (the detection sequence X includes multiple sub-detection sequences, and the baud rates of these multiple sub-detection sequences carried by the first optical signal are equal, which is the baud rate of the detection sequence X); the optical receiving device determines the distance between the two reflection points corresponding to the secondary peak on the optical fiber link Z based on the transmission duration, and then determines the fault point on the optical fiber link Z based on the distance between the two reflection points. For example, poor contact caused by dirt on the end face of the connector on fiber optic link Z or a loose connector can lead to reflection of the optical signal at the connector. The reflection point on fiber optic link Z is usually located at the connector. The optical receiving equipment determines the fault point on fiber optic link Z based on the distance between the two reflection points corresponding to the secondary peak and the deployment of fiber optic link Z.

[0269] The time-shift symbol difference corresponding to the second peak may be positive or negative. When the time-shift symbol difference is positive, the optical receiving device determines the transmission duration of the reflected optical signal between the two reflection points corresponding to the second peak by multiplying the time-shift symbol difference corresponding to the second peak by the symbol period (i.e., the reciprocal of the baud rate) of the detection sequence X carried by the first optical signal. When the time-shift symbol difference corresponding to the second peak is negative, the optical receiving device determines the sum of the time-shift symbol difference corresponding to the second peak and the length of the target sequence. The optical receiving device then determines the number of delay symbols corresponding to the second peak by multiplying the number of delay symbols corresponding to the second peak by the symbol period (i.e., the reciprocal of the baud rate) of the detection sequence X carried by the first optical signal. The target sequence is the sequence used in obtaining the correlation curve corresponding to the detection sequence X demodulated from the second optical signal. The target sequence can be the detection sequence X or any sub-detection sequence included in the detection sequence X.

[0270] In an optional embodiment, for each of the at least one secondary peak: the optical receiving device determines the distance between the two reflection points corresponding to the secondary peak on the optical fiber link Z using a distance-time formula based on the transmission duration of the reflected optical signal between the two reflection points corresponding to the secondary peak. For example, the distance-time formula is S = v * T / 2. v represents the transmission speed of the optical signal in the optical fiber link Z, T represents the transmission duration of the reflected optical signal between the two reflection points corresponding to the secondary peak, S represents the distance between the two reflection points corresponding to the secondary peak, and the symbol "*" represents multiplication and the symbol " / " represents division. In an optional embodiment, the laser end face of the optical transmitting device has strong reflectivity, and can be considered as a fixed reflection point. In this case, "S" in the distance-time formula represents the distance between a fault point in the optical fiber link Z (the fault point corresponding to the secondary peak) and the optical transmitting device (specifically, the distance between the fault point corresponding to the secondary peak and the laser end face of the optical transmitting device). The optical receiving device determines the distance between the two reflection points corresponding to the secondary peak, which in turn determines the distance between the fault point corresponding to the secondary peak and the laser end face of the optical transmitting device, that is, it determines the location of the fault point corresponding to the secondary peak.

[0271] Please refer to Figure 26 This diagram illustrates the correlation curve corresponding to the detection sequence X demodulated from the second optical signal by the optical receiving device. This correlation curve is either an autocorrelation curve or a cross-correlation curve. See also... Figure 26 The correlation curve has two characteristic peaks, and the correlation value at all other points on the curve besides these two characteristic peaks is 0. Figure 26 As an example only, in practical applications, due to the influence of random noise, the autocorrelation values ​​at all points on the correlation curve other than the characteristic peak are all very low noise floors; that is, the correlation values ​​at all points on the correlation curve other than the characteristic peak are very small but may not be zero. Assuming the laser endface of the optical transmitting device has strong reflectivity and is a fixed reflection point, the optical receiving device determines that there is a fault in the fiber optic link Z based on the characteristic peak of the correlation curve. Furthermore, as... Figure 26As shown, the two characteristic peaks include a primary peak and a secondary peak. The time-shifted symbol count corresponding to the primary peak is 0, and the time-shifted symbol count corresponding to the secondary peak is 6. Therefore, the optical receiving device determines the time-shifted symbol difference corresponding to the secondary peak to be 6 (6-0=6). The optical receiving device uses the product of the time-shifted symbol difference corresponding to the secondary peak and the symbol period of the detection sequence X carried by the first optical signal to determine the transmission duration of the reflected optical signal between the two reflection points (the end face of the laser of the optical transmitting device and a fault point) corresponding to the secondary peak. Based on this transmission duration, the optical receiving device uses the aforementioned distance-time formula to determine the distance between the two reflection points corresponding to the secondary peak. Based on the distance between the two reflection points and the position of the end face of the laser of the optical transmitting device, the optical receiving device determines the fault point on the optical fiber link Z corresponding to the secondary peak.

[0272] In an optional embodiment, if the correlation curve corresponding to the detection sequence X demodulated from the second optical signal has multiple characteristic peaks, the optical receiving device further determines the strength of the reflection intensity of the reflection point (including fault points) corresponding to each of the multiple characteristic peaks based on the peak value of each secondary peak. For example, the vertical axis of the correlation curve corresponding to the detection sequence X demodulated from the second optical signal represents the correlation degree (i.e., the correlation value), and the peak value of each secondary peak reflects the strength of the reflection intensity of the reflection point corresponding to that secondary peak. The peak value of the secondary peak is positively correlated with the strength of the reflection intensity of the reflection point corresponding to that secondary peak. The larger the peak value of the secondary peak, the stronger the reflection intensity of the reflection point corresponding to that secondary peak. The smaller the peak value of the secondary peak, the weaker the reflection intensity of the reflection point corresponding to that secondary peak. The strength of the reflection intensity is also referred to as the reflection strength.

[0273] In this embodiment, the optical receiving device can not only determine whether there is a fault in the optical fiber link Z based on the correlation curve corresponding to the detection sequence X demodulated from the second optical signal, but also, if a fault is determined in the optical fiber link Z, the optical receiving device can determine the fault point on the optical fiber link Z based on the characteristic peak of the correlation curve, thus achieving fault location of the optical fiber link Z. Therefore, in this embodiment, no personnel are required to carry instruments to the site for fault location, making the process simple. Furthermore, if a fault is determined in the optical fiber link Z, the optical receiving device can also determine the strength of the reflection degree of the reflection point (including the fault point) corresponding to the secondary peak from the peak value of the correlation curve corresponding to the detection sequence X demodulated from the second optical signal, thereby qualitatively determining the degree of fault at the fault point. Specifically, the larger the peak value of the secondary peak, the stronger the reflection degree of the reflection point (including the fault point) corresponding to the secondary peak, and the greater the degree of fault at the fault point. Conversely, the smaller the peak value of the secondary peak, the weaker the reflection degree of the reflection point (including the fault point) corresponding to the secondary peak, and the less severe the fault at the fault point.

[0274] In this embodiment, the correlation curve corresponding to the detection sequence X demodulated from the second optical signal can be an autocorrelation curve or a cross-correlation curve. The detection sequence X includes multiple sub-detection sequences (e.g., sub-detection sequences X1 to Xn). The autocorrelation curve corresponding to the detection sequence X demodulated from the second optical signal is determined based on the autocorrelation curves of the multiple demodulated sub-detection sequences, and the autocorrelation curve of each sub-detection sequence demodulated from the second optical signal is determined based on each demodulated sub-detection sequence. The cross-correlation curve corresponding to the detection sequence X demodulated from the second optical signal is determined based on the cross-correlation curves of the multiple demodulated sub-detection sequences, and the cross-correlation curve of each sub-detection sequence demodulated from the second optical signal is determined based on each demodulated sub-detection sequence and each sub-detection sequence known to the optical receiving device.

[0275] In one embodiment, the correlation curve corresponding to the detection sequence X demodulated from the second optical signal is an autocorrelation curve. The detection sequence X includes sub-detection sequences X1 to Xn, which are demodulated from the second optical signal by the optical receiving device. For each sub-detection sequence X1 to Xn demodulated from the second optical signal: the optical receiving device performs autocorrelation calculation on the demodulated sub-detection sequence to obtain its autocorrelation curve. The optical receiving device can obtain multiple autocorrelation curves corresponding one-to-one with the demodulated sub-detection sequences X1 to Xn. For example, these multiple autocorrelation curves are referred to as autocorrelation curves 1 to n, and autocorrelation curves 1 to n correspond one-to-one with sub-detection sequences X1 to Xn. Autocorrelation curve 1 is the autocorrelation curve of the demodulated sub-detection sequence X1. Autocorrelation curve 2 is the autocorrelation curve of the demodulated sub-detection sequence X2, and so on. Autocorrelation curve n is the autocorrelation curve of the demodulated sub-detection sequence Xn. The optical receiving device determines the autocorrelation curve corresponding to the demodulated detection sequence X based on autocorrelation curves 1 to n. The autocorrelation curve corresponding to the demodulated detection sequence X can be a superposition curve of autocorrelation curves 1 to n. In a specific embodiment, the position points on autocorrelation curves 1 to n (also the position points corresponding to the time shift sign numbers) correspond one-to-one. The optical receiving device adds the amplitudes (i.e., autocorrelation values) on autocorrelation curves 1 to n according to the corresponding position points. The optical receiving device plots a curve based on the added amplitudes (i.e., autocorrelation values) to obtain the autocorrelation curve corresponding to the demodulated detection sequence X. In one example, autocorrelation curves 1 to n all include position points -w to w, each position point in -w to w corresponds to a time shift sign number, where w is a positive integer. The position points -w to w on autocorrelation curves 1 to n correspond one-to-one. The optical receiving device sums the n amplitudes (i.e., n autocorrelation values) corresponding to n positions -w on the autocorrelation curve 1 to n (each of these n positions -w corresponds to a position on the autocorrelation curve 1 to n) to obtain the superimposed amplitude corresponding to position -w. The optical receiving device sums the n amplitudes (i.e., n autocorrelation values) corresponding to n positions -w+1 (each of these n positions -w+1 corresponds to a position on the autocorrelation curve 1 to n) to obtain the superimposed amplitude corresponding to position -w+1. The optical receiving device sums the n amplitudes (i.e., n autocorrelation values) corresponding to n positions -w+2 (each of these n positions -w+2 corresponds to a position on the autocorrelation curve 1 to n) to obtain the superimposed amplitude corresponding to position -w+2. Similarly, the optical receiving device adds up the n amplitudes (i.e. n autocorrelation values) corresponding to the n position points w on the autocorrelation curve 1 to n (each of the n position points w is located on the autocorrelation curve 1 to n) to obtain the superimposed amplitude corresponding to that position point w.The optical receiving device can determine the superimposed amplitude corresponding to each position point -w to w. Based on the position points -w to w and their corresponding superimposed amplitudes, the optical receiving device plots a curve, which is the autocorrelation curve corresponding to the demodulated detection sequence X. In this embodiment, the target sequence mentioned in the previous embodiment can be any one of the sub-detection sequences X1 to Xn demodulated from the second optical signal by the optical receiving device.

[0276] In another embodiment, the correlation curve corresponding to the detection sequence X demodulated from the second optical signal is a cross-correlation curve. The detection sequence X includes sub-detection sequences X1 to Xn, which are demodulated from the second optical signal by the optical receiving device. For each sub-detection sequence X1 to Xn demodulated from the second optical signal: the optical receiving device performs cross-correlation calculation between the demodulated sub-detection sequence and the sub-detection sequence known to the optical receiving device to obtain the cross-correlation curve of the sub-detection sequence. The optical receiving device can obtain multiple cross-correlation curves corresponding one-to-one with the demodulated sub-detection sequences X1 to Xn. For example, these multiple cross-correlation curves are referred to as cross-correlation curves 1 to n, and cross-correlation curves 1 to n correspond one-to-one with the sub-detection sequences X1 to Xn. Cross-correlation curve 1 is the cross-correlation curve of sub-detection sequence X1 (specifically, the cross-correlation curve between the demodulated sub-detection sequence X1 and the sub-detection sequence X1 known to the optical receiving device). Cross-correlation curve 2 is the cross-correlation curve of sub-detection sequence X2 (specifically, the cross-correlation curve between the demodulated sub-detection sequence X2 and the sub-detection sequence X2 known to the optical receiving device). And so on. Cross-correlation curve n is the cross-correlation curve of sub-detection sequence Xn (specifically, the cross-correlation curve between the demodulated sub-detection sequence Xn and the sub-detection sequence Xn known to the optical receiving device). The optical receiving device determines the cross-correlation curve corresponding to the demodulated detection sequence X based on cross-correlation curves 1 to n. The cross-correlation curve corresponding to the demodulated detection sequence X can be a superposition curve of cross-correlation curves 1 to n. In a specific embodiment, the position points on cross-correlation curves 1 to n (also the position points corresponding to the time shift sign number) correspond one-to-one. The optical receiving device adds the amplitude values ​​(i.e., cross-correlation values) on cross-correlation curves 1 to n according to the corresponding position points. The optical receiving device plots a curve based on the added amplitude values ​​(i.e., cross-correlation values) to obtain the cross-correlation curve corresponding to the demodulated detection sequence X from the second optical signal. In one example, the cross-correlation curves 1 to n all include position points -w to w, each position point corresponding to a time shift symbol number, where w is a positive integer. Position points -w to w on the cross-correlation curves 1 to n correspond one-to-one. The optical receiving device sums the n amplitude values ​​(i.e., n cross-correlation values) corresponding to the n position points -w on the cross-correlation curves 1 to n (each of these n position points -w corresponds to a position on the cross-correlation curves 1 to n) to obtain the superimposed amplitude value corresponding to position point -w. The optical receiving device sums the n amplitude values ​​(i.e., n cross-correlation values) corresponding to the n position points -w+1 on the cross-correlation curves 1 to n (each of these n position points -w+1 corresponds to a position on the cross-correlation curves 1 to n) to obtain the superimposed amplitude value corresponding to position point -w+1. The optical receiving device adds up the n amplitude values ​​(i.e. n cross-correlation values) corresponding to the n position points -w+2 (each of the n position points -w+2 is located on the cross-correlation curve 1 to n) on the cross-correlation curve 1 to n to obtain the superimposed amplitude value corresponding to the position point -w+2.Similarly, the optical receiving device adds the n amplitudes (i.e., n cross-correlation values) corresponding to the n position points w (each of which corresponds to a position on the cross-correlation curve 1 to n) on the cross-correlation curve 1 to n to obtain the superimposed amplitude corresponding to that position point w. The optical receiving device can determine the superimposed amplitude corresponding to position points -w to w, and plot a curve based on the position points -w to w and the superimposed amplitude corresponding to them. The curve plotted by the optical receiving device is the cross-correlation curve corresponding to the detection sequence X demodulated from the second optical signal. In this embodiment, the target sequence mentioned in the previous embodiment can be any one of the sub-detection sequences X1 to Xn demodulated from the second optical signal by the optical receiving device, or it can be any one of the sub-detection sequences X1 to Xn known to the optical receiving device. This application embodiment does not limit this.

[0277] The above embodiments illustrate how an optical receiving device determines the correlation curve corresponding to a demodulated detection sequence X from a second optical signal based on the correlation curve of the sub-detection sequences X1 to Xn demodulated from the second optical signal. In an optional embodiment, the optical receiving device obtains the demodulated detection sequence X based on the demodulated sub-detection sequences X1 to Xn (e.g., the optical receiving device concatenates the demodulated sub-detection sequences X1 to Xn to obtain the demodulated detection sequence X), and performs correlation calculations on the demodulated detection sequence X to obtain the correlation curve corresponding to the demodulated detection sequence X. In one embodiment, the correlation curve is an autocorrelation curve, and the optical receiving device performs autocorrelation calculations on the demodulated detection sequence X to obtain the autocorrelation curve corresponding to the demodulated detection sequence X. For this embodiment, the aforementioned target sequence can be the demodulated detection sequence X. In another embodiment, the correlation curve is a cross-correlation curve, and the optical receiving device performs cross-correlation calculations on the demodulated detection sequence X and a known detection sequence X to obtain the cross-correlation curve corresponding to the demodulated detection sequence X. In this other embodiment, the aforementioned target sequence can be a demodulated detection sequence X, or a detection sequence X known to the optical receiving device. In optional embodiments, such as... Figure 13 , Figure 14 and Figure 19 As shown, the optical receiving device also includes a correlation calculation unit, which determines the correlation curve corresponding to the demodulated detection sequence X based on the demodulated sub-detection sequences X1 to Xn.

[0278] To facilitate understanding of the implementation process of S305, the following two examples will be used to introduce the implementation principle of S305.

[0279] In one example, the first optical signal carries a detection sequence X, which includes sub-detection sequences X1 to Xn. These sub-detection sequences X1 to Xn are carried in the first optical signal using wavelength division multiplexing (WDM) or parallel-fiber multiplexing. The first optical signal includes sub-optical signals F1 to Fn, each corresponding one-to-one with the sub-detection sequences X1 to Xn. Each sub-optical signal F1 to Fn carries multiple corresponding sub-detection sequences, and these multiple corresponding sub-detection sequences are periodically distributed. For ease of description, we will take the example where each sub-optical signal F1 to Fn carries only a sub-detection sequence. Then, the sub-optical signals F1 to Fn can be represented as: F1 = [X1 X1 X1 X1 X1 X1…]; F2 = [X2 X2 X2 X2 X2 X2…]; …; Fn = [Xn Xn Xn Xn Xn Xn…]. The optical transmitting device sends the first optical signal to the optical receiving device through the optical fiber link Z.

[0280] Without considering noise, attenuation, and faults in the fiber optic link Z, the first optical signal remains unchanged during transmission in the fiber optic link Z, and the optical receiving device receives the first optical signal. The optical receiving device demodulates the first optical signal to obtain sub-detection sequences X1 to Xn. The optical receiving device acquires the correlation curve of each sub-detection sequence in the demodulated sub-detection sequences X1 to Xn. The optical receiving device determines the correlation curve corresponding to the demodulated detection sequence X based on the correlation curves of the demodulated sub-detection sequences X1 to Xn. For example, the sub-detection sequences X1 to Xn are as follows: Figures 4 to 7 The sub-detection sequences X1 to X4 are shown below. The correlation curve of sub-detection sequence X1 is as follows: Figure 8 The autocorrelation curve shown is similar to the correlation curve of the sub-detection sequence X2. Figure 9 The autocorrelation curve shown is similar to the correlation curve of the sub-detection sequence X3. Figure 10 The autocorrelation curve shown is similar to the correlation curve of the sub-detection sequence X4. Figure 11 The autocorrelation curve shown is used. The correlation curve corresponding to the demodulated detection sequence X, determined by the optical receiving device based on the correlation curves of the demodulated sub-detection sequences X1 to Xn, can be as follows: Figure 12 The autocorrelation curve shown is as follows. Figure 12 As shown, the correlation curve has a characteristic peak, and the amplitude of all other points on the correlation curve except for the characteristic peak is 0.

[0281] However, fiber optic links Z inevitably experience noise, attenuation, and faults, causing the first optical signal to transform into a second optical signal after transmission through fiber optic link Z. The optical receiving device then receives this second optical signal. For example, the second optical signal includes sub-optical signals G1 to Gn, which correspond one-to-one with sub-optical signals F1 to Fn. Sub-optical signal G1 includes sub-optical signal F1 and the sub-reflected optical signal R1 generated by sub-optical signal F1 transmitted in fiber optic link Z. Sub-optical signal G2 includes sub-optical signal F2 and the sub-reflected optical signal R2 generated by sub-optical signal F2 transmitted in fiber optic link Z. Similarly, sub-optical signal Gn includes sub-optical signal Fn and the sub-reflected optical signal Rn generated by sub-optical signal Fn transmitted in fiber optic link Z. The sub-reflected optical signals R1 to Rn can be expressed as: R1 = β*F1(t-t0); R2 = β*F2(t-t0); ..., Rn = β*Fn(t-t0). The sub-optical signals G1 to Gn can be expressed as: G1 = F1 + R1, G2 = F2 + R2, ..., Gn = Fn + Rn. t0 represents the delay time between the sub-reflected optical signal and its corresponding transmitted sub-optical signal (sub-optical signals F1 to Fn are all transmitted sub-optical signals) in reaching the optical receiving device; that is, the time difference between the moment the sub-reflected optical signal reaches the optical receiving device and the moment the corresponding transmitted sub-optical signal reaches the optical receiving device. β represents the attenuation coefficient of the sub-reflected optical signal (the formation of this sub-reflected optical signal is caused by multiple reflections of the transmitted sub-optical signal by reflection points in the fiber optic link Z). If there are multiple reflection points in the fiber optic link Z, the right-hand side of the expression for the sub-reflected optical signals R1 to Rn will have multiple terms, each representing a different delay time between the sub-reflected optical signal and its corresponding transmitted sub-optical signal in reaching the optical receiving device, and the attenuation coefficient may also be different. The optical receiving device demodulates the second optical signal to obtain the sub-detection sequences X1 to Xn. The optical receiving device acquires the correlation curve of each sub-detection sequence X1 to Xn from the demodulated sub-detection sequences. Based on the correlation curves of the demodulated sub-detection sequences X1 to Xn, the optical receiving device determines the correlation curve corresponding to the demodulated detection sequence X. For example, the sub-detection sequences X1 to Xn are as follows: Figures 4 to 7 The sub-detection sequences X1 to X4 are shown. The correlation curve corresponding to the demodulated detection sequence X is determined by the optical receiving device based on the correlation curve of the demodulated sub-detection sequences X1 to Xn, as shown in the figure. Figure 26 As shown. See also Figure 26 This correlation curve not only has similar Figure 12The characteristic peak (main peak) shown also has a secondary peak. This secondary peak is generated by the superposition of the autocorrelation of the sub-reflected optical signals R1~Rn (e.g., sub-reflected optical signals R1~R4), or by the superposition of the cross-correlation of the sub-reflected optical signals R1~R4 with the known sub-detection sequences X1~X4. Therefore, the transmission duration of the reflected optical signal between the two reflection points corresponding to the secondary peak can be determined based on the difference between the number of time-shifted symbols corresponding to the main peak and the number of time-shifted symbols corresponding to the secondary peak. Furthermore, the reflection point (fault point) corresponding to the secondary peak on the optical fiber link Z can be determined based on this transmission duration.

[0282] In another example, the first optical signal carries a detection sequence X, which includes sub-detection sequences X1 to Xn. These sub-detection sequences X1 to Xn are carried in the first optical signal in a time-division multiplexed manner. Each sub-detection sequence X1 to Xn corresponds one-to-one with a time period T1 to Tn. The first optical signal carries multiple corresponding sub-detection sequences in each time period, and these multiple corresponding sub-detection sequences are periodically distributed. For ease of description, let's take the example where the first optical signal only carries the detection sequence. The first optical signal can be represented as: F = [X1 X1 X1 X1 X1 X1…X2 X2 X2 X2 X2 X2…Xn Xn Xn Xn Xn Xn…]. The optical transmitting device sends the first optical signal to the optical receiving device through the optical fiber link Z.

[0283] Without considering noise, attenuation, and faults in the fiber optic link Z, the first optical signal remains unchanged during transmission in the fiber optic link Z, and the optical receiving device receives the first optical signal. The optical receiving device demodulates the first optical signal to obtain sub-detection sequences X1 to Xn. The optical receiving device acquires the correlation curve of each sub-detection sequence in the demodulated sub-detection sequences X1 to Xn. The optical receiving device determines the correlation curve corresponding to the demodulated detection sequence X based on the correlation curves of the demodulated sub-detection sequences X1 to Xn. For example, the sub-detection sequences X1 to Xn are as follows: Figures 4 to 7 The sub-detection sequences X1 to X4 are shown below. The correlation curve of sub-detection sequence X1 is as follows: Figure 8 The autocorrelation curve shown is similar to the correlation curve of the sub-detection sequence X2. Figure 9 The autocorrelation curve shown is similar to the correlation curve of the sub-detection sequence X3. Figure 10 The autocorrelation curve shown is similar to the correlation curve of the sub-detection sequence X4. Figure 11 The autocorrelation curve shown is used. The correlation curve corresponding to the demodulated detection sequence X, determined by the optical receiving device based on the correlation curves of the demodulated sub-detection sequences X1 to Xn, can be as follows: Figure 12 The autocorrelation curve shown is as follows. Figure 12 As shown, the correlation curve has a characteristic peak, and the amplitude of all other points on the correlation curve except for the characteristic peak is 0.

[0284] However, fiber optic links Z inevitably suffer from noise, attenuation, and faults, causing the first optical signal to transform into a second optical signal after transmission through link Z. The optical receiving device then receives the second optical signal. The second optical signal comprises the first optical signal and a reflected optical signal R. The reflected optical signal R can be expressed as: R = β*F(t-t0). The second optical signal can be expressed as: G = F + R. t0 represents the delay time between the reflected optical signal R and the first optical signal reaching the optical receiving device; that is, the time difference between the arrival time of the reflected optical signal R and the arrival time of the first optical signal. β represents the attenuation coefficient of the reflected optical signal R (multiple reflections of the first optical signal by reflection points in fiber optic link Z result in the formation of the reflected optical signal R; β is the attenuation coefficient caused by these multiple reflections). If there are multiple reflection points in fiber optic link Z, the right-hand side of the above expression for the reflected optical signal R will contain multiple terms, each representing a different delay time between the reflected optical signal and the first optical signal reaching the optical receiving device, and potentially different attenuation coefficients. The optical receiving device demodulates the second optical signal to obtain the sub-detection sequences X1 to Xn. The optical receiving device acquires the correlation curve of each sub-detection sequence X1 to Xn from the demodulated sub-detection sequences. Based on the correlation curves of the demodulated sub-detection sequences X1 to Xn, the optical receiving device determines the correlation curve corresponding to the demodulated detection sequence X. For example, the sub-detection sequences X1 to Xn are as follows: Figures 4 to 7 The sub-detection sequences X1 to X4 are shown. The correlation curve corresponding to the demodulated detection sequence X is determined by the optical receiving device based on the correlation curve of the demodulated sub-detection sequences X1 to Xn, as shown in the figure. Figure 26 As shown. See also Figure 26 This correlation curve not only has similar Figure 12 The characteristic peak (main peak) shown also has a secondary peak. This secondary peak is generated by the superposition of the autocorrelation of the sub-reflected optical signals R1~Rn (e.g., sub-reflected optical signals R1~R4), or by the superposition of the cross-correlation of the sub-reflected optical signals R1~R4 with the known sub-detection sequences X1~X4. Therefore, the transmission duration of the reflected optical signal between the two reflection points corresponding to the secondary peak can be determined based on the difference between the number of time-shifted symbols corresponding to the main peak and the number of time-shifted symbols corresponding to the secondary peak. Furthermore, the reflection point (fault point) corresponding to the secondary peak on the optical fiber link Z can be determined based on this transmission duration.

[0285] In optional embodiments, after the optical receiving device determines the transmission performance of the optical fiber link Z based on the demodulated detection sequence X, for example, after the optical receiving device determines that there is a fault in the optical fiber link Z, the optical receiving device issues a fault warning. In one example, the optical receiving device controls its indicator light to flash or illuminate to issue a fault warning. In another example, the optical receiving device outputs warning information to a device with a display component and / or a voice broadcast component to issue a fault warning. The device with the display component and / or voice broadcast component can present the warning information through display or voice broadcast to issue a fault warning; this application embodiment does not limit this approach.

[0286] It should be noted that both optical transmitting and receiving devices can include optical modules and / or optical fiber cards. Figure 3 In the description of the illustrated embodiment, all or part of the operations performed by the optical transmitting device are specifically performed by the optical module and / or optical fiber card in the optical transmitting device, and all or part of the operations performed by the optical receiving device are specifically performed by the optical module and / or optical fiber card in the optical receiving device. For example Figure 13 , Figure 14 and Figure 19 Both the optical transmitting device 210 and the optical receiving device 220 shown include optical modules or optical fiber cards. In the optical transmitting device 210, the optical transmitter, optical multiplexer, etc., can be located on the optical module or optical fiber card. In the optical receiving device 220, the optical demultiplexer, optical receiver, demodulation unit, and related computing unit, etc., can be located on the optical module or optical fiber card. Furthermore, as... Figure 13 , Figure 14 and Figure 19 As shown, the optical transmitting device 210 and the optical receiving device 220 are also connected to a control device, which can control the optical transmitting device 210 and the optical receiving device 220. For example, the control device controls the optical transmitting device 210 to send a first optical signal carrying a detection sequence to the optical receiving device 220 through the optical fiber link Z; the control device controls the optical receiving device 220 to receive a second optical signal through the optical fiber link Z; the control device controls the optical receiving device 220 to demodulate the second optical signal to obtain the detection sequence; and the control device controls the optical receiving device 220 to determine the transmission performance of the optical fiber link Z based on the demodulated detection sequence. As another example, after the optical receiving device 220 determines the transmission performance of the optical fiber link Z based on the demodulated detection sequence X, it can send the transmission performance information of the optical fiber link Z to the control device, which can then present the transmission performance information of the optical fiber link Z (e.g., the control device provides a fault warning based on the transmission performance information of the optical fiber link Z).

[0287] Based on the above description, the embodiments of this application can use either in-band detection or out-of-band detection to detect the transmission performance of an optical fiber link. In-band detection, also known as in-path detection or online detection, refers to transmitting the detection sequence and data signal along the same optical signal through the optical fiber link to detect the transmission performance of the optical fiber link based on the detection sequence. Out-of-band detection, also known as offline detection, refers to transmitting the detection sequence along an independent optical signal (i.e., the detection sequence and data signal are carried in different optical signals) through the optical fiber link to detect the transmission performance of the optical fiber link based on the detection sequence. The detection method for the transmission performance of the optical fiber link can be controlled by a control device. In-path detection can achieve online detection of the transmission performance of the optical fiber link and provide online early warning for the optical fiber link. In optional embodiments, the optical transmitting device and the optical receiving device further include switching units, which are used to switch between the data signal and the detection sequence. Specifically, the switching unit in the optical transmitting device controls the optical transmitting device to modulate the optical signal using a detection sequence or a data signal; the switching unit in the optical receiving device controls the optical receiving device to demodulate the detection sequence or data signal from the optical signal. For example, in detection mode, the switching unit in the optical transmitting device controls the optical transmitting device to modulate the optical signal using a detection sequence, and the switching unit in the optical receiving device controls the optical receiving device to demodulate the detection sequence from the optical signal. In non-detection mode, the switching unit in the optical transmitting device controls the optical transmitting device to modulate the optical signal using a data signal, and the optical receiving device demodulates the data signal from the optical signal. The operation of the switching unit can also be controlled by a control device.

[0288] This application supports wavelength division multiplexing, parallel fiber multiplexing, and time division multiplexing.

[0289] In wavelength division multiplexing (WDM), multiple sub-optical signals comprising a first optical signal are transmitted simultaneously through the same optical fiber in the fiber optic link. This same fiber has the same influence on all sub-optical signals, and they experience the same physical environment during transmission. WDM helps save fiber optic resources, thus offering significant benefits in long-distance fiber optic communication systems. For example, a 400G-LR4 optical module multiplexes four sub-optical signals of different wavelengths to obtain a single optical signal, which can then be transmitted over a distance of up to 10 km (kilometers) via a single optical fiber. "400G-LR4" refers to the module's specification. The 400G-LR4 optical module is a 400 gigabit Ethernet (GE) optical module. The full English name of 400G-LR4 is 400 gigabit Ethernet-longreach4. The full Chinese name of 400G-LR is 400 gigabit Ethernet-long reach 4.

[0290] In parallel fiber multiplexing, the optical fiber link comprises multiple parallel optical fibers. Multiple sub-optical signals, including the first optical signal, are transmitted simultaneously through these fibers in a one-to-one correspondence. These fibers can be encapsulated in the same optical cable. The same MPO connector on the cable has the same effect on these fibers, thus affecting the multiple sub-optical signals transmitted simultaneously within them equally. These sub-optical signals experience the same physical environment during transmission. Parallel fiber multiplexing requires relatively more optical fiber resources; therefore, it is typically used in short-distance optical fiber communication systems. For example, a 400G-SR8 optical module can utilize eight optical fibers to transmit 400GE optical signals, with each fiber transmitting 50GE optical signals. "400G-SR8" refers to the module's specification. The 400G-SR8 optical module is a type of 400GE optical module. The full English name of 400G-SR8 is 400 gigabit Ethernet-short reach 8. The full Chinese name of 400G-SR8 is 400 gigabit Ethernet-short reach 8.

[0291] In time-division multiplexing (TDM), the first optical signal carries different sub-detection sequences comprising the detection sequence in a time-division manner. TDM is applicable to both long-distance and short-distance optical fiber communication systems. Furthermore, TDM helps save storage space for storing the detection sequences. Specifically, in TDM, the multiple sub-detection sequences included in the detection sequence correspond one-to-one with multiple time periods. The optical transmitting device transmits a first optical signal carrying the corresponding sub-detection sequence in each time period. Therefore, in each time period, the storage space used to store the detection sequence only needs to store the corresponding sub-detection sequence, instead of storing all multiple sub-detection sequences, thus saving storage space. Alternatively, the storage space used to store the detection sequences can be set smaller to save storage resources. The storage space used to store the detection sequences can be random access memory (RAM) storage space.

[0292] Furthermore, with a fixed storage space for storing detection sequences, time-division multiplexing helps increase the fault detection distance (e.g., increasing the distance between the fault point that can be located on the optical fiber link and the optical transmitting device), enabling long-distance fault location. Specifically, the aforementioned distance-time formula "S = v * T / 2" can also be called the fault location formula. In this formula, v represents the transmission speed of the optical signal in the optical fiber link, and S and T correspond to the same secondary peak on the correlation curve of the detection sequence demodulated by the optical receiving device from the second optical signal. This secondary peak corresponds to two reflection points on the optical fiber link, S represents the distance between the two reflection points, and T represents the transmission duration of the reflected optical signal between the two reflection points. T is equal to the pr...

Claims

1. A method for detecting an optical fiber link, characterized in that, Applied to an optical transmitting device, the method includes: A first optical signal is generated, the first optical signal carries a detection sequence, the detection sequence is used by the optical receiving device to detect the transmission performance of the optical fiber link, the detection sequence includes multiple sub-detection sequences, the multiple sub-detection sequences are carried in the first optical signal in a multiplexed manner; The first optical signal is transmitted to the optical receiving device via the optical fiber link. The first optical signal is then transmitted through the optical fiber link between the optical transmitting device and the optical receiving device and becomes a second optical signal. The second optical signal includes the first optical signal and a reflected optical signal.

2. The method according to claim 1, characterized in that, The reuse method includes any of the following: Wavelength division multiplexing, parallel fiber multiplexing, or time division multiplexing.

3. The method according to claim 2, characterized in that, The multiplexing method is wavelength division multiplexing. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with a multiple sub-detection sequence, and any two of the multiple sub-optical signals have different wavelengths; The optical fiber link includes a first optical fiber, which is used to transmit the plurality of sub-optical signals.

4. The method according to claim 2, characterized in that, The reuse method is a parallel fiber reuse method; The first optical signal includes multiple sub-optical signals, and each of the multiple sub-optical signals corresponds one-to-one with the multiple sub-detection sequences; The optical fiber link includes a first optical fiber and a second optical fiber in parallel. The first optical fiber is used to transmit a first sub-optical signal, and the second optical fiber is used to transmit a second sub-optical signal. The plurality of sub-optical signals include the first sub-optical signal and the second sub-optical signal.

5. The method according to claim 4, characterized in that, The first optical fiber and the second optical fiber satisfy the following: The length of the first optical fiber is the same as the length of the second optical fiber; The connector on the first optical fiber is located at the same position as the connector on the second optical fiber.

6. The method according to any one of claims 3 to 5, characterized in that, The plurality of sub-detection sequences include a first sub-detection sequence, the plurality of sub-optical signals include a first sub-optical signal, the first sub-optical signal corresponds to the first sub-detection sequence, the first sub-optical signal carries a plurality of the first sub-detection sequences, and the plurality of the first sub-detection sequences are periodically distributed in the first sub-optical signal; There are boundary markers between adjacent first sub-detection sequences in multiple first sub-detection sequences; or, Adjacent first sub-detection sequences in a plurality of first sub-detection sequences are consecutive.

7. The method according to claim 2, characterized in that, The multiplexing method is time-division multiplexing. The first optical signal carries a first sub-detection sequence in a first time period, and the first optical signal carries a second sub-detection sequence in a second time period. The plurality of sub-detection sequences include the first sub-detection sequence and the second sub-detection sequence.

8. The method according to claim 7, characterized in that, The first optical signal carries multiple first sub-detection sequences during the first time period, and the multiple first sub-detection sequences are periodically distributed in the first optical signal; There are boundary markers between adjacent first sub-detection sequences in multiple first sub-detection sequences; or, Adjacent first sub-detection sequences in a plurality of first sub-detection sequences are consecutive.

9. The method according to any one of claims 1 to 8, characterized in that, The first optical signal also carries a data signal.

10. The method according to any one of claims 1 to 9, characterized in that, The autocorrelation curve corresponding to the detection sequence meets a preset condition, and the autocorrelation curve corresponding to the detection sequence is determined based on the autocorrelation curves of the plurality of sub-detection sequences.

11. A method for detecting an optical fiber link, characterized in that, Applied to an optical receiving device, the method includes: The second optical signal is received through the optical fiber link. The second optical signal includes a first optical signal and a reflected optical signal. The first optical signal is an optical signal generated by the optical transmitting device. The first optical signal carries a detection sequence. The detection sequence includes multiple sub-detection sequences. The multiple sub-detection sequences are carried in the first optical signal in a multiplexed manner. The second optical signal is demodulated to obtain the detection sequence; The transmission performance of the optical fiber link is determined based on the demodulated detection sequence.

12. The method according to claim 11, characterized in that, The reuse method includes any of the following: Wavelength division multiplexing, parallel fiber multiplexing, or time division multiplexing.

13. The method according to claim 12, characterized in that, The multiplexing method is wavelength division multiplexing. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with a multiple sub-detection sequence, and any two of the multiple sub-optical signals have different wavelengths; The optical fiber link includes a first optical fiber, which is used to transmit the plurality of sub-optical signals.

14. The method according to claim 12, characterized in that, The reuse method is a parallel fiber reuse method; The first optical signal includes multiple sub-optical signals, and each of the multiple sub-optical signals corresponds one-to-one with the multiple sub-detection sequences; The optical fiber link includes a first optical fiber and a second optical fiber in parallel. The first optical fiber is used to transmit a first sub-optical signal, and the second optical fiber is used to transmit a second sub-optical signal. The plurality of sub-optical signals include the first sub-optical signal and the second sub-optical signal.

15. The method according to claim 14, characterized in that, The first optical fiber and the second optical fiber satisfy the following: The length of the first optical fiber is the same as the length of the second optical fiber; The connector on the first optical fiber is located at the same position as the connector on the second optical fiber.

16. The method according to any one of claims 13 to 15, characterized in that, The plurality of sub-detection sequences include a first sub-detection sequence, the plurality of sub-optical signals include a first sub-optical signal, the first sub-optical signal corresponds to the first sub-detection sequence, the first sub-optical signal carries a plurality of the first sub-detection sequences, and the plurality of the first sub-detection sequences are periodically distributed in the first sub-optical signal; There are boundary markers between adjacent first sub-detection sequences in multiple first sub-detection sequences; or, Adjacent first sub-detection sequences in a plurality of first sub-detection sequences are consecutive.

17. The method according to claim 16, characterized in that, The first sub-optical signal carries multiple first detection sub-sequences, and there are boundary markers between adjacent first sub-detection sequences among the multiple first sub-detection sequences; After the first sub-optical signal is transmitted via the optical fiber link, it becomes a third sub-optical signal. The third sub-optical signal includes the first sub-optical signal and the first sub-reflected optical signal. The second optical signal includes the third sub-optical signal. The reflected optical signal includes the first sub-reflected optical signal. The demodulation of the second optical signal to obtain the detection sequence includes: The first sub-detection sequence carried by the third sub-optical signal is determined based on the boundary identifier carried by the third sub-optical signal.

18. The method according to claim 16, characterized in that, The first sub-optical signal carries multiple first detection sub-sequences, and adjacent first sub-detection sequences among the multiple first sub-detection sequences are consecutive. After the first sub-optical signal is transmitted via the optical fiber link, it becomes a third sub-optical signal. The third sub-optical signal includes the first sub-optical signal and the first sub-reflected optical signal. The second optical signal includes the third sub-optical signal. The reflected optical signal includes the first sub-reflected optical signal. The demodulation of the second optical signal to obtain the detection sequence includes: Based on the characteristics of the first sub-detection sequence, the first sub-detection sequence carried by the third sub-optical signal is determined.

19. The method according to claim 12, characterized in that, The multiplexing method is time-division multiplexing. The first optical signal carries a first sub-detection sequence in a first time period, and the first optical signal carries a second sub-detection sequence in a second time period. The plurality of sub-detection sequences include the first sub-detection sequence and the second sub-detection sequence.

20. The method according to claim 19, characterized in that, The first optical signal carries multiple first sub-detection sequences during the first time period, and the multiple first sub-detection sequences are periodically distributed in the first optical signal; There are boundary markers between adjacent first sub-detection sequences in multiple first sub-detection sequences; or, Adjacent first sub-detection sequences in a plurality of first sub-detection sequences are consecutive.

21. The method according to claim 20, characterized in that, The first optical signal carries multiple first sub-detection sequences during the first time period, and there are boundary markers between adjacent first sub-detection sequences among the multiple first sub-detection sequences; The demodulation of the second optical signal to obtain the detection sequence includes: The first sub-detection sequence carried by the second optical signal is determined based on the boundary identifier carried by the second optical signal.

22. The method according to claim 20, characterized in that, The first optical signal carries multiple first sub-detection sequences during the first time period, and adjacent first sub-detection sequences among the multiple first sub-detection sequences are consecutive; The demodulation of the second optical signal to obtain the detection sequence includes: Based on the characteristics of the first sub-detection sequence, the first sub-detection sequence carried by the second optical signal is determined.

23. The method according to any one of claims 11 to 22, characterized in that, The step of demodulating the second optical signal to obtain the detection sequence includes: demodulating the second optical signal to obtain the plurality of sub-detection sequences; Determining the transmission performance of the optical fiber link based on the demodulated detection sequence includes: Obtain the correlation curve of each demodulated sub-detection sequence, wherein the correlation curve is an autocorrelation curve or a cross-correlation curve, and the cross-correlation curve of each demodulated sub-detection sequence is determined based on each demodulated sub-detection sequence and each known sub-detection sequence; Based on the correlation curves of the demodulated multiple sub-detection sequences, determine the correlation curve corresponding to the demodulated detection sequence; The transmission performance of the optical fiber link is determined based on the correlation curve corresponding to the demodulated detection sequence.

24. The method according to claim 23, characterized in that, The autocorrelation curve corresponding to the detection sequence satisfies a preset condition, and the step of determining the transmission performance of the optical fiber link based on the demodulated correlation curve corresponding to the detection sequence includes: The transmission performance of the optical fiber link is determined based on the correlation curve corresponding to the demodulated detection sequence and the preset conditions.

25. The method according to any one of claims 11 to 24, characterized in that, The first optical signal also carries a data signal.

26. A detection device for an optical fiber link, characterized in that, The detection device, applied to optical transmitting equipment, includes: A generation module is used to generate a first optical signal, the first optical signal carrying a detection sequence, the detection sequence being used by an optical receiving device to detect the transmission performance of the optical fiber link, the detection sequence including multiple sub-detection sequences, the multiple sub-detection sequences being carried in the first optical signal in a multiplexed manner; The transmitting module is used to transmit the first optical signal to the optical receiving device through the optical fiber link. The first optical signal is transmitted through the optical fiber link between the optical transmitting device and the optical receiving device and then becomes a second optical signal. The second optical signal includes the first optical signal and a reflected optical signal.

27. The detection device according to claim 26, characterized in that, The reuse method includes any of the following: Wavelength division multiplexing, parallel fiber multiplexing, or time division multiplexing.

28. The detection device according to claim 27, characterized in that, The multiplexing method is wavelength division multiplexing. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with a multiple sub-detection sequence, and any two of the multiple sub-optical signals have different wavelengths; The optical fiber link includes a first optical fiber, which is used to transmit the plurality of sub-optical signals.

29. The detection device according to claim 27, characterized in that, The reuse method is a parallel fiber reuse method; The first optical signal includes multiple sub-optical signals, and each of the multiple sub-optical signals corresponds one-to-one with the multiple sub-detection sequences; The optical fiber link includes a first optical fiber and a second optical fiber in parallel. The first optical fiber is used to transmit a first sub-optical signal, and the second optical fiber is used to transmit a second sub-optical signal. The plurality of sub-optical signals include the first sub-optical signal and the second sub-optical signal.

30. The detection device according to claim 29, characterized in that, The first optical fiber and the second optical fiber satisfy the following: The length of the first optical fiber is the same as the length of the second optical fiber; The connector on the first optical fiber is located at the same position as the connector on the second optical fiber.

31. The detection apparatus according to any one of claims 28 to 30, characterized in that, The plurality of sub-detection sequences include a first sub-detection sequence, the plurality of sub-optical signals include a first sub-optical signal, the first sub-optical signal corresponds to the first sub-detection sequence, the first sub-optical signal carries a plurality of the first sub-detection sequences, and the plurality of the first sub-detection sequences are periodically distributed in the first sub-optical signal; There are boundary markers between adjacent first sub-detection sequences in multiple first sub-detection sequences; or, Adjacent first sub-detection sequences in a plurality of first sub-detection sequences are consecutive.

32. The detection device according to claim 27, characterized in that, The multiplexing method is time-division multiplexing. The first optical signal carries a first sub-detection sequence in a first time period, and the first optical signal carries a second sub-detection sequence in a second time period. The plurality of sub-detection sequences include the first sub-detection sequence and the second sub-detection sequence.

33. The detection device according to claim 32, characterized in that, The first optical signal carries multiple first sub-detection sequences during the first time period, and the multiple first sub-detection sequences are periodically distributed in the first optical signal; There are boundary markers between adjacent first sub-detection sequences in multiple first sub-detection sequences; or, Adjacent first sub-detection sequences in a plurality of first sub-detection sequences are consecutive.

34. The detection apparatus according to any one of claims 26 to 33, characterized in that, The first optical signal also carries a data signal.

35. The detection apparatus according to any one of claims 26 to 34, characterized in that, The autocorrelation curve corresponding to the detection sequence meets a preset condition, and the autocorrelation curve corresponding to the detection sequence is determined based on the autocorrelation curves of the plurality of sub-detection sequences.

36. A detection device for an optical fiber link, characterized in that, The detection device, applied to an optical receiving device, includes: A receiving module is configured to receive a second optical signal via the optical fiber link. The second optical signal includes a first optical signal and a reflected optical signal. The first optical signal is an optical signal generated by an optical transmitting device. The first optical signal carries a detection sequence, which includes multiple sub-detection sequences. The multiple sub-detection sequences are carried in the first optical signal in a multiplexed manner. A demodulation module is used to demodulate the second optical signal to obtain the detection sequence; A determination module is used to determine the transmission performance of the optical fiber link based on the demodulated detection sequence.

37. The detection device according to claim 36, characterized in that, The reuse method includes any of the following: Wavelength division multiplexing, parallel fiber multiplexing, or time division multiplexing.

38. The detection device according to claim 37, characterized in that, The multiplexing method is wavelength division multiplexing. The first optical signal includes multiple sub-optical signals, each of which corresponds one-to-one with a multiple sub-detection sequence, and any two of the multiple sub-optical signals have different wavelengths; The optical fiber link includes a first optical fiber, which is used to transmit the plurality of sub-optical signals.

39. The detection device according to claim 37, characterized in that, The reuse method is a parallel fiber reuse method; The first optical signal includes multiple sub-optical signals, and each of the multiple sub-optical signals corresponds one-to-one with the multiple sub-detection sequences; The optical fiber link includes a first optical fiber and a second optical fiber in parallel. The first optical fiber is used to transmit a first sub-optical signal, and the second optical fiber is used to transmit a second sub-optical signal. The plurality of sub-optical signals include the first sub-optical signal and the second sub-optical signal.

40. The detection device according to claim 39, characterized in that, The first optical fiber and the second optical fiber satisfy the following: The length of the first optical fiber is the same as the length of the second optical fiber; The connector on the first optical fiber is located at the same position as the connector on the second optical fiber.

41. The detection apparatus according to any one of claims 38 to 40, characterized in that, The plurality of sub-detection sequences include a first sub-detection sequence, the plurality of sub-optical signals include a first sub-optical signal, the first sub-optical signal corresponds to the first sub-detection sequence, the first sub-optical signal carries a plurality of the first sub-detection sequences, and the plurality of the first sub-detection sequences are periodically distributed in the first sub-optical signal; There are boundary markers between adjacent first sub-detection sequences in multiple first sub-detection sequences; or, Adjacent first sub-detection sequences in a plurality of first sub-detection sequences are consecutive.

42. The detection device according to claim 41, characterized in that, The first sub-optical signal carries multiple first detection sub-sequences, and there are boundary markers between adjacent first sub-detection sequences among the multiple first sub-detection sequences; After the first sub-optical signal is transmitted via the optical fiber link, it becomes a third sub-optical signal. The third sub-optical signal includes the first sub-optical signal and the first sub-reflected optical signal. The second optical signal includes the third sub-optical signal. The reflected optical signal includes the first sub-reflected optical signal. The demodulation module is used to determine the first sub-detection sequence carried by the third sub-optical signal based on the boundary identifier carried by the third sub-optical signal.

43. The detection device according to claim 41, characterized in that, The first sub-optical signal carries multiple first detection sub-sequences, and adjacent first sub-detection sequences among the multiple first sub-detection sequences are consecutive. After the first sub-optical signal is transmitted via the optical fiber link, it becomes a third sub-optical signal. The third sub-optical signal includes the first sub-optical signal and the first sub-reflected optical signal. The second optical signal includes the third sub-optical signal. The reflected optical signal includes the first sub-reflected optical signal. The demodulation module is used to determine the first sub-detection sequence carried by the third sub-optical signal based on the characteristics of the first sub-detection sequence.

44. The detection device according to claim 37, characterized in that, The multiplexing method is time-division multiplexing. The first optical signal carries a first sub-detection sequence in a first time period, and the first optical signal carries a second sub-detection sequence in a second time period. The plurality of sub-detection sequences include the first sub-detection sequence and the second sub-detection sequence.

45. The detection device according to claim 44, characterized in that, The first optical signal carries multiple first sub-detection sequences during the first time period, and the multiple first sub-detection sequences are periodically distributed in the first optical signal; There are boundary markers between adjacent first sub-detection sequences in multiple first sub-detection sequences; or, Adjacent first sub-detection sequences in a plurality of first sub-detection sequences are consecutive.

46. ​​The detection device according to claim 45, characterized in that, The first optical signal carries multiple first sub-detection sequences during the first time period, and there are boundary markers between adjacent first sub-detection sequences among the multiple first sub-detection sequences; The demodulation module is used to determine the first sub-detection sequence carried by the second optical signal based on the boundary identifier carried by the second optical signal.

47. The detection device according to claim 45, characterized in that, The first optical signal carries multiple first sub-detection sequences during the first time period, and adjacent first sub-detection sequences among the multiple first sub-detection sequences are consecutive; The demodulation module is used to determine the first sub-detection sequence carried by the second optical signal based on the characteristics of the first sub-detection sequence.

48. The detection apparatus according to any one of claims 36 to 47, characterized in that, The demodulation module is used to demodulate the second optical signal to obtain the plurality of sub-detection sequences; The determining module is used for: Obtain the correlation curve of each demodulated sub-detection sequence, wherein the correlation curve is an autocorrelation curve or a cross-correlation curve, and the cross-correlation curve of each demodulated sub-detection sequence is determined based on each demodulated sub-detection sequence and each known sub-detection sequence; Based on the correlation curves of the demodulated multiple sub-detection sequences, determine the correlation curve corresponding to the demodulated detection sequence; The transmission performance of the optical fiber link is determined based on the correlation curve corresponding to the demodulated detection sequence.

49. The detection device according to claim 48, characterized in that, The autocorrelation curve corresponding to the detection sequence meets the preset conditions. The determining module is used to determine the transmission performance of the optical fiber link based on the correlation curve corresponding to the demodulated detection sequence and the preset conditions.

50. The detection apparatus according to any one of claims 36 to 49, characterized in that, The first optical signal also carries a data signal.

51. A detection device for an optical fiber link, characterized in that, Including memory and processor; The memory is used to store computer programs; The processor is configured to execute a computer program stored in the memory to cause the detection device to perform at least some of the steps in the method as described in any one of claims 1 to 25.

52. A detection device for an optical fiber link, characterized in that, Including processors and optical devices; The optical device is used to perform the transmit / receive operation in the method as described in any one of claims 1 to 25; The processor is used to perform operations other than the send / receive operation in the method as described in any one of claims 1 to 25.

53. The detection device according to claim 52, characterized in that, The processor includes an optical digital signal processor (ODSP); The optical device includes at least one of an optical transmitter or an optical receiver.

54. The detection device according to claim 52 or 53, characterized in that, The detection device is an optical module or an optical fiber card.

55. An optical fiber communication system, characterized in that, It includes an optical transmitting device, an optical receiving device, and an optical fiber link, wherein the optical transmitting device and the optical receiving device are connected via the optical fiber link; The optical transmitting device includes the detection device as described in any one of claims 26 to 35, 51 to 54; The optical receiving device includes the detection device as described in any one of claims 36 to 54.

56. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed, implements at least some of the steps in the method as described in any one of claims 1 to 25.

57. A computer program product, characterized in that, The computer program product includes a program or code that, when executed, implements at least some of the steps in the method as described in any one of claims 1 to 25.

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