A method for obtaining time delay difference, receiving device and measurement system

Abstract

The embodiment of the present invention discloses a method for obtaining a delay difference, a receiving device, and a measurement system, which can improve the accuracy and efficiency of the obtained delay difference. The method of the embodiment of the present invention includes: the receiving device receives a first optical signal from a sending device via a first transmission channel; the receiving device receives a second optical signal from a sending device via a second transmission channel; the receiving device samples the beat signal of the first optical signal and the second optical signal to obtain the phase of N sampled signals; the receiving device obtains a first delay difference based on the phase of the N sampled signals, and the first delay difference is the difference between the delay of the first optical signal transmitted via the first transmission channel and the delay of the second optical signal transmitted via the second transmission channel.

Description

Technical Field

[0001] The present application relates to the field of optical fiber communications, and in particular to a method for obtaining a time delay difference, a receiving device, and a measuring system. Background Art

[0002] Delay is an important transmission indicator in optical communication systems, which is used to feedback the time it takes for a signal to be sent and received. If there are multiple delays between the sending device and the receiving device, the difference between the delays is also important.

[0003] To this end, the delay difference between two devices can be measured according to the precision clock synchronization protocol standard for network measurement and control systems (IEEE 1588). Among them, the first device and the second device are connected by two optical fibers (i.e., the first optical fiber and the second optical fiber). The delay difference refers to the difference between the delay of the first optical signal from the first device transmitted via the first optical fiber and the delay of the second optical signal from the second device transmitted via the second optical fiber. In order to measure the delay difference, IEEE 1588 requires the first device to modulate the first timestamp in the first optical signal, and the second device to modulate the second timestamp in the second optical signal. The first device obtains the delay difference based on the first timestamp and the second timestamp.

[0004] Modulating the timestamp in the optical signal requires the support of the upper-layer protocol, and the process of measuring the delay difference includes the processing time of the upper-layer protocol, resulting in low accuracy of the calculated delay difference. Summary of the invention

[0005] The embodiments of the present invention provide a method for obtaining a time delay difference, a receiving device and a measuring system, which can improve the accuracy and efficiency of the obtained time delay difference.

[0006] In a first aspect, an embodiment of the present invention provides a method for obtaining a delay difference, the method comprising: a receiving device receives a first optical signal from a sending device via a first transmission channel; the receiving device receives a second optical signal from the sending device via a second transmission channel. The first transmission channel and the second transmission channel are respectively connected between the sending device and the receiving device. The receiving device samples the beat frequency signals of the first optical signal and the second optical signal to obtain the phases of N sampled signals. The phases of the N sampled signals are the phases obtained by sampling the beat frequency signals at N different sampling times, respectively, and N is a positive integer greater than 1. The receiving device obtains a first delay difference based on the phases of the N sampled signals. The first delay difference is the difference between the delay of the first optical signal transmitted via the first transmission channel and the delay of the second optical signal transmitted via the second transmission channel.

[0007] It can be seen that the beat signal is formed by mixing the first optical signal and the second optical signal by the receiving device. Then, the beat signal reflects the correlation between the first optical signal and the second optical signal. The receiving device obtains the first delay difference based on the beat signal that reflects the correlation between the first optical signal and the second optical signal, thereby improving the accuracy of obtaining the first delay difference. Moreover, in the process of obtaining the first delay difference, there is no need for the sending device and the receiving device to modulate the timestamp in the optical signal, nor is there a need for the sending device and the receiving device to demodulate the optical signal to obtain the timestamp. It can be seen that the process of obtaining the first delay difference does not need to be supported by the upper layer protocol, thereby improving the efficiency of obtaining the first delay difference. Moreover, since there is no need for the upper layer protocol to be processed, the first delay difference obtained does not include the time for the upper layer protocol to be processed, thereby effectively improving the accuracy of the first delay difference obtained.

[0008] In the process of obtaining the first time delay difference, no other equipment is required. For example, no optical time domain reflectometer (OTDR) is required, which reduces the cost of measuring the first time delay difference. Since obtaining the time delay difference through OTDR requires manual operation, the method shown in this aspect does not require manual participation, which improves the reliability and accuracy of measuring the first time delay difference.

[0009] Based on the first aspect, in an optional implementation, the first optical signal and the second optical signal are homologous optical signals, wherein the homologous optical signals mean that the first optical signal and the second optical signal are generated by the same laser in the sending device at the same time.

[0010] It can be seen that the process in which the receiving device obtains the first time delay difference based on the first optical signal and the second optical signal of the same source effectively improves the efficiency and accuracy of obtaining the first time delay difference.

[0011] Based on the first aspect, in an optional implementation, a difference between an optical frequency of the first optical signal and an optical frequency of the second optical signal is less than or equal to a preset value to ensure that a receiving device can successfully acquire a beat frequency signal.

[0012] Based on the first aspect, in an optional implementation, the first optical signal and the second optical signal satisfy a polarization condition. The polarization condition means that the minimum angle difference between the polarization state of the first optical signal and the polarization state of the second optical signal is any angle greater than or equal to 0 and less than 90 degrees, so as to ensure that the receiving device can successfully acquire the beat frequency signal.

[0013] Based on the first aspect, in an optional implementation method, the receiving device obtains a first delay difference based on the phase of the N sampling signals, including: the receiving device determines that the difference between the first phase sequence and the second phase sequence is a differential phase sequence. The first phase sequence includes the phases of k sampling signals among the N sampling signals. The second phase sequence includes the phases of j sampling signals among the N sampling signals. k is equal to j, and the sampling moments of the phases of two sampling signals in the same sequence order in the first phase sequence and the second phase sequence are different. The receiving device obtains the first delay difference according to the differential phase sequence.

[0014] Among them, the accuracy of the measured first time delay difference can be adjusted as shown in this aspect, and the receiving device can change the measurement time range of the receiving device by changing the value of N in the phase of the N sampling signals obtained by sampling. The value of N is positively correlated with the measurement time range of the receiving device. It can be seen that the larger the value of N, the longer the measurement time range. If the first time delay difference is within the measurement time range of the receiving device, the receiving device can accurately measure the first time delay difference. Moreover, if the receiving device needs to improve the accuracy of the first time delay difference obtained, the receiving device can increase the sampling frequency of sampling the beat frequency signal.

[0015] Based on the first aspect, in an optional implementation, the phases of the k sampling signals included in the first phase sequence are continuously taken in sequence order among the N sampling signal phases. The phases of the j sampling signals included in the second phase sequence are continuously taken in sequence order among the N sampling signal phases.

[0016] Based on the first aspect, in an optional implementation, the phases of the k sampling signals included in the first phase sequence are arranged at intervals among the phases of the N sampling signals. The phases of the j sampling signals included in the second phase sequence are arranged at intervals among the phases of the N sampling signals. The time interval between the phases of any two adjacent sampling signals in the first phase sequence is equal to the time interval between the phases of any two adjacent sampling signals in the second phase sequence.

[0017] Based on the first aspect, in an optional implementation, the time interval between sampling moments of the phases of any two adjacent sampling signals in the first phase sequence is equal to the time interval between sampling moments of the phases of any two adjacent sampling signals in the second phase sequence.

[0018] Based on the first aspect, in an optional implementation, the receiving device obtains the first time delay difference according to the differential phase sequence, including: the receiving device performs Fourier transform on the differential phase sequence to obtain a power spectrum density PSD of the differential phase sequence. The receiving device obtains the first time delay difference from the PSD of the differential phase sequence.

[0019] Based on the first aspect, in an optional implementation method, the receiving device obtains the first time delay difference from the PSD of the differential phase sequence, including: the receiving device performs Fourier transform on the PSD of the differential phase sequence to obtain the first time delay difference.

[0020] Based on the first aspect, in an optional implementation method, after the receiving device obtains the first delay difference based on the phase of the N sampling signals, it also includes: the receiving device receives a third optical signal from the sending device via a third transmission channel. The third transmission channel includes an optical device. The receiving device receives a fourth optical signal from the sending device via the second transmission channel; the receiving device obtains a second delay difference. The second delay difference is the difference between the delay of the third optical signal transmitted via the third transmission channel and the delay of the fourth optical signal transmitted via the fourth transmission channel. If the second delay difference is greater than the first delay difference, the receiving device determines that the transmission delay of the first transmission channel is less than the transmission delay of the second transmission channel.

[0021] It can be seen that the receiving device can obtain the relationship between the transmission delay of the first transmission channel and the transmission delay of the second transmission channel, and then determine which of the optical signals transmitted via the first transmission channel and the optical signal transmitted via the second transmission channel will arrive at the receiving device first when the sending device sends two optical signals of the same source to the receiving device, so as to obtain the transmission status of the optical signal transmitted between the sending device and the receiving device.

[0022] Based on the first aspect, in an optional implementation method, after the receiving device obtains the second delay difference, it also includes: the receiving device determines that the delay of the optical device is the absolute value of the difference between the first delay difference and the second delay difference.

[0023] It can be seen that when it is necessary to measure the delay of an optical device, the optical device can be connected to a third transmission channel, so as to obtain the delay of the optical device based on the first delay difference and the second delay difference. In the process of measuring the delay of an optical device, there is no need to use equipment such as OTDR, which reduces the cost of measuring the delay of the optical device. Moreover, in the process of obtaining the first delay difference and the second delay difference, there is no need for the sending device to modulate the timestamp in each optical signal, and there is no need for the receiving device to demodulate the optical signals from the sending device to obtain the timestamp. In the process of obtaining the first delay difference and the second delay difference, there is no need to obtain the support of the upper layer protocol, which improves the accuracy of obtaining the delay of the optical device.

[0024] Based on the first aspect, in an optional implementation, the receiving device obtains a target length difference according to the first delay difference and the target refractive index. The target length difference is the difference between the length of the first transmission channel and the length of the second transmission channel. Specifically, the receiving device obtains the target length difference according to the following formula.

[0025] It can be seen that based on the first delay difference between the first transmission channel and the second transmission channel, the target length difference between the length of the first transmission channel and the length of the second transmission channel can be obtained, so as to determine the actual networking situation between the sending device and the receiving device, obtain the link status, and improve the consistency of evaluating the transmission channel length between the first transmission channel and the second transmission channel.

[0026] In a second aspect, an embodiment of the present invention provides a receiving device, the receiving device comprising a receiving module and a processing module connected to the receiving module; the receiving module is used to receive a first optical signal from a sending device via a first transmission channel; the receiving module is also used to receive a second optical signal from the sending device via a second transmission channel. The first transmission channel and the second transmission channel are respectively connected between the sending device and the receiving device; the processing module is used to sample the beat frequency signals of the first optical signal and the second optical signal to obtain the phases of N sampled signals. The phases of the N sampled signals are the phases obtained by sampling the beat frequency signals at N different sampling times, respectively, and N is a positive integer greater than 1. The processing module is also used to obtain a first delay difference based on the phases of the N sampled signals. The first delay difference is the difference between the delay of the first optical signal transmitted via the first transmission channel and the delay of the second optical signal transmitted via the second transmission channel.

[0027] For the description of the beneficial effects of this aspect, please refer to Example 1, which will not be repeated here.

[0028] Based on the second aspect, in an optional implementation, the processing module is specifically used to: determine the difference between the first phase sequence and the second phase sequence as a differential phase sequence in the process of obtaining the first time delay difference based on the phase of the N sampling signals. The first phase sequence includes the phases of k sampling signals among the N sampling signals. The second phase sequence includes the phases of j sampling signals among the N sampling signals. k is equal to j, and the sampling moments of the phases of the two sampling signals in the same sequence order in the first phase sequence and the second phase sequence are different. The first time delay difference is obtained according to the differential phase sequence.

[0029] Based on the second aspect, in an optional implementation, the time interval between sampling moments of the phases of any two adjacent sampling signals in the first phase sequence is equal to the time interval between sampling moments of the phases of any two adjacent sampling signals in the second phase sequence.

[0030] Based on the second aspect, in an optional implementation method, the processing module, in the process of obtaining the first time delay difference according to the differential phase sequence, is specifically used to: perform Fourier transform on the differential phase sequence to obtain the power spectral density PSD of the differential phase sequence; and obtain the first time delay difference from the PSD of the differential phase sequence.

[0031] Based on the second aspect, in an optional implementation, the processing module, in the process of acquiring the first time delay difference from the PSD of the differential phase sequence, is specifically used to: perform Fourier transform on the PSD of the differential phase sequence to acquire the first time delay difference.

[0032] Based on the second aspect, in an optional implementation, the processing module is further used to: receive a third optical signal from the sending device via a third transmission channel, the third transmission channel including an optical device. Receive a fourth optical signal from the sending device via the second transmission channel; and obtain a second delay difference. The second delay difference is the difference between the delay of the third optical signal transmitted via the third transmission channel and the delay of the fourth optical signal transmitted via the fourth transmission channel; if the second delay difference is greater than the first delay difference, it is determined that the transmission delay of the first transmission channel is less than the transmission delay of the second transmission channel.

[0033] Based on the second aspect, in an optional implementation, the processing module is further used to: determine the delay of the optical device as an absolute value of a difference between the first delay difference and the second delay difference.

[0034] In a third aspect, an embodiment of the present invention provides a measurement system, the measurement system comprising a transmitting device and a receiving device, and further comprising a first transmission channel and a second transmission channel connected between the transmitting device and the receiving device. The receiving device is used to receive a first optical signal from the transmitting device via the first transmission channel. The receiving device is also used to receive a second optical signal from the transmitting device via the second transmission channel, and the first transmission channel and the second transmission channel are respectively connected between the transmitting device and the receiving device. The receiving device is also used to sample the beat frequency signal of the first optical signal and the second optical signal to obtain the phases of N sampled signals. The phases of the N sampled signals are the phases obtained by sampling the beat frequency signal at N different sampling times, respectively, and N is a positive integer greater than 1. The receiving device is also used to obtain a first delay difference based on the phases of the N sampled signals, and the first delay difference is the difference between the delay of the first optical signal transmitted via the first transmission channel and the delay of the second optical signal transmitted via the second transmission channel.

[0035] For the description of the beneficial effects of this aspect, please refer to the first aspect and the details will not be repeated here.

[0036] Based on the third aspect, in an optional implementation, the measurement system further includes a spectrometer module, which is connected to the sending device. The spectrometer module is also connected to the first transmission channel and the second transmission channel respectively. The spectrometer module is used to: receive an optical signal from the sending device; split the optical signal to obtain the first optical signal and the second optical signal; transmit the first optical signal to the first transmission channel; and transmit the second optical signal to the second transmission channel.

[0037] Based on the third aspect, in an optional implementation, the receiving device is used to: determine the difference between the first phase sequence and the second phase sequence as a differential phase sequence in the process of obtaining the first time delay difference based on the phase of the N sampling signals. The first phase sequence includes the phases of k sampling signals among the N sampling signals. The second phase sequence includes the phases of j sampling signals among the N sampling signals. k is equal to j, and the sampling moments of the phases of the two sampling signals in the same sequence order in the first phase sequence and the second phase sequence are different; the first time delay difference is obtained according to the differential phase sequence.

[0038] Based on the third aspect, in an optional implementation, the time interval between sampling moments of the phases of any two adjacent sampling signals in the first phase sequence is equal to the time interval between sampling moments of the phases of any two adjacent sampling signals in the second phase sequence.

[0039] Based on the third aspect, in an optional implementation method, the receiving device obtains the first time delay difference according to the differential phase sequence, specifically for: performing Fourier transform on the differential phase sequence to obtain the power spectrum density PSD of the differential phase sequence; and obtaining the first time delay difference from the PSD of the differential phase sequence.

[0040] Based on the third aspect, in an optional implementation, in the process of the receiving device acquiring the first time delay difference from the PSD of the differential phase sequence, it is specifically used to: perform Fourier transform on the PSD of the differential phase sequence to acquire the first time delay difference.

[0041] Based on the third aspect, in an optional implementation, the measurement system further includes a third transmission channel, and the third transmission channel includes an optical device. The receiving device is also used to: receive a third optical signal from the sending device via the third transmission channel; receive a fourth optical signal from the sending device via the second transmission channel; and obtain a second delay difference, wherein the second delay difference is the difference between the delay of the third optical signal transmitted via the third transmission channel and the delay of the fourth optical signal transmitted via the fourth transmission channel. If the second delay difference is greater than the first delay difference, it is determined that the transmission delay of the first transmission channel is less than the transmission delay of the second transmission channel.

[0042] Based on the third aspect, in an optional implementation, the measurement system further includes a reflection module and a deflection module, the deflection module is connected between the optical device and the receiving device, and the optical device is connected to the reflection module. The first port of the deflection module is used to receive the third optical signal from the sending device. The second port of the deflection module is used to transmit the third optical signal to the third port of the optical device. The fourth port of the optical device is used to transmit the third optical signal to the reflection module. The reflection module is used to reflect the third optical signal to transmit the third optical signal to the fourth port of the optical device. The third port of the optical device is used to transmit the third optical signal to the second port of the deflection module. The fifth port of the deflection module is used to transmit the third optical signal to the receiving device.

[0043] Based on the third aspect, in an optional implementation, the receiving device is also used to: determine the delay of the optical device as the absolute value of the difference between the first delay difference and the second delay difference.

[0044] It can be seen from the above technical solutions that the embodiments of the present invention have the following advantages:

[0045] A method for obtaining a delay difference, a receiving device and a measuring system provided by an embodiment of the present invention, wherein the receiving device can mix a first optical signal and a second optical signal from a sending device to form a beat signal. It can be seen that the beat signal reflects the correlation between the first optical signal and the second optical signal. The receiving device obtains the first delay difference based on the beat signal reflecting the correlation between the first optical signal and the second optical signal, thereby improving the accuracy of obtaining the first delay difference. Moreover, in the process of obtaining the first delay difference, there is no need for the sending device and the receiving device to modulate the timestamp in the optical signal, nor is there a need for the sending device and the receiving device to demodulate the optical signal to obtain the timestamp. It can be seen that the process of obtaining the first delay difference does not need to be supported by the upper layer protocol, thereby improving the efficiency of obtaining the first delay difference. Moreover, since there is no need for the upper layer protocol to process, the first delay difference obtained does not include the time of the upper layer protocol processing, thereby effectively improving the accuracy of the first delay difference obtained. In the process of obtaining the first delay difference, there is no need to use other devices, thereby reducing the cost of measuring the first delay difference. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a structural example diagram of the first embodiment of the measurement system provided in this application;

[0047] Figure 2 A flowchart of the first embodiment of the method for obtaining the delay difference provided by the present application;

[0048] Figure 3 A flowchart of the steps of the second embodiment of the method for obtaining the delay difference provided by the present application;

[0049] Figure 4A A flowchart of the steps of the third embodiment of the method for obtaining the delay difference provided by the present application;

[0050] Figure 4B This is an example diagram of the first application scenario of the method for obtaining the delay difference provided in this application;

[0051] Figure 5 A flowchart of the fourth embodiment of the method for obtaining the delay difference provided by the present application;

[0052] Figure 6 This is an example diagram of a second application scenario of the method for obtaining the delay difference provided in this application;

[0053] Figure 7 This is an example diagram of a third application scenario of the method for obtaining the delay difference provided in this application;

[0054] Figure 8 A flowchart of the fifth embodiment of the method for obtaining the delay difference provided by the present application;

[0055] Fig. 9 This is a diagram showing an example structure of a first embodiment of a receiving device provided in this application;

[0056] Fig.10 This is a diagram showing an example structure of the second embodiment of the receiving device provided in this application. DETAILED DESCRIPTION

[0057] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0058] To better understand the method for obtaining the delay difference provided by the present application, the following first combines Figure 1 The measurement system used in the method provided in this application is described as shown in the figure: wherein, Figure 1 This is a structural example diagram of the first embodiment of the measurement system provided in this application.

[0059] This embodiment does not limit the application scenario of the measurement system. For example, the measurement system shown in this embodiment can be applied to a passive optical network (PON), a transport network, an all-optical data center network, a metropolitan area network, or a wireless bearer network.

[0060] The measurement system shown in this embodiment includes a sending device 101, and the sending device 101 includes a laser. The laser is used to emit an optical signal. The sending device 101 is connected to a spectrometer module 102, and the spectrometer module 102 can be a fiber coupler, also known as a spectrometer. Specifically, the sending device 101 and the spectrometer module 102 are connected through a transmission channel 110. The transmission channel 110 can be an optical cable, an optical waveguide, or an optical waveguide device. Among them, when light propagates in free space, it is dispersed due to diffraction, and the refractive index of the optical waveguide device is higher than the refractive index of free space. Since the optical signal is repeatedly totally reflected on the interface of the optical waveguide device, the optical signal can be confined to the space of the optical waveguide device for transmission to ensure that the optical waveguide device can transmit the optical signal from the sending device 101 to the spectrometer module 102.

[0061] The optical splitter module 102 has an input port and a first output port and a second output port. The input port is connected to the transmission channel 110. The first output port is connected to the first transmission channel 111, and the second output port is connected to the second transmission channel 112. Among them, the first transmission channel 110 and the second transmission channel 112 are two transmission channels connected between the optical splitter module 102 and the receiving device 103, and the length of the first transmission channel 111 is not equal to the length of the second transmission channel 112. For the specific description of the types of the first transmission channel 110 and the second transmission channel 112 in this embodiment, please refer to the description of the transmission channel 110, and the details are not repeated here. The optical splitter module is used to couple the optical signal from the transmission channel 110 to the first transmission channel 111 and the second transmission channel 112, respectively. This embodiment does not limit the ratio between the optical power of the first optical signal coupled to the first transmission channel 111 by the optical splitter module 102 and the optical power of the second optical signal coupled to the second transmission channel by the optical splitter module 102. It should be noted that this embodiment does not limit the magnitude of the optical power of the first optical signal and the magnitude of the optical power of the second optical signal, but it is necessary to ensure that the receiving device 103 can successfully receive the first optical signal and the second optical signal.

[0062] The optical splitter module 102 shown in this embodiment may also be an optical filter. Specifically, the optical filter may be a polarizing plate. The first optical signal can pass through the polarizing plate to enter the first transmission channel 111 for transmission. The second optical signal is reflected by the polarizing plate to enter the second transmission channel 112 for transmission.

[0063] This embodiment is described by taking the example that the optical splitter module 102 is connected between the sending device 101 and the receiving device 103. In other examples, the optical splitter module 102 may also be arranged in the sending device 101. The sending device 101 and the receiving device 103 are connected through the first transmission channel and the second transmission channel respectively, so that the sending device 101 directly transmits the first optical signal and the second optical signal to the receiving device 103 via the first transmission channel and the second transmission channel.

[0064] Embodiment 1

[0065] based on Figure 1 The measurement system shown below is combined with Figure 2 The execution process of the method for obtaining the delay difference provided by the present application is described as follows. Figure 2 This is a flowchart of the first embodiment of the method for obtaining the delay difference provided in the present application.

[0066] Step 201: A receiving device receives a first optical signal from a sending device via a first transmission channel.

[0067] For example, the expression of the first optical signal shown in this embodiment can refer to the following expression 1:

[0068] Expression 1:

[0069] Among them, E R1 (t) represents the first optical signal. A1 represents the amplitude of the first optical signal transmitted by the first transmission channel. exp is an exponential function with the natural constant e as the base. and is a complex symbol. τ1 represents the time delay of the first optical signal transmitted via the first transmission channel. ω c ×(t-τ1) represents the relationship between t-τ1 and angular frequency ω c The product of . represents the phase noise of the first optical signal varying with t-τ1.

[0070] It should be noted that the expression 1 shown in this embodiment is an example, not a limitation. In other examples, parameters may be added or reduced, or coefficients in the current expression 1 may be changed, etc., without specific limitation.

[0071] Step 202: The receiving device receives a second optical signal from the sending device via a second transmission channel.

[0072] For a description of the first and second transmission channels, see Figure 1 The relevant descriptions shown are not elaborated in detail. It can be seen that the first optical signal and the second optical signal are independently transmitted to the receiving device via the first transmission channel and the second transmission channel respectively. The receiving device can synchronously receive the first optical signal and the second optical signal via the first transmission channel and the second transmission channel. The first optical signal and the second optical signal shown in this embodiment are homologous optical signals. Among them, the homologous optical signal means that the first optical signal and the second optical signal are generated by the same laser in the sending device at the same time. Specifically, in combination Figure 1 As shown, the laser included in the sending device 101 transmits an optical signal to the optical splitting module 102 via the transmission channel 110 , and the first optical signal and the second optical signal are generated by the optical splitting module 102 splitting the optical signal from the laser.

[0073] For example, the expression of the second optical signal shown in this embodiment can refer to the following expression 2:

[0074] Expression 2:

[0075] Among them, E R2 (t) represents the second optical signal. A2 represents the amplitude of the second optical signal transmitted by the second transmission channel. τ2 represents the time delay of the second optical signal transmitted via the second transmission channel. ω c ×(t-τ2) represents the relationship between t-τ2 and angular frequency ω c The product of . represents the phase noise of the second optical signal varying with t-τ2.

[0076] It should be noted that the expression 2 shown in this embodiment is an example, not a limitation. In other examples, parameters may be added or reduced, or the coefficients in the current expression 2 may be changed, etc., without specific limitation.

[0077] Step 203: The receiving device performs beat frequency processing on the first optical signal and the second optical signal to obtain a beat frequency signal.

[0078] The receiving device shown in this embodiment mixes the first optical signal and the second optical signal to obtain a beat signal. The beat signal shown in this embodiment can also be called a beat wave signal, a difference frequency signal, etc. The embodiment of the present application does not impose any restriction on the name of the beat signal.

[0079] In order to successfully obtain the beat signal in this embodiment, the first optical signal and the second optical signal need to meet the polarization condition. The polarization condition means that the minimum angle difference between the polarization state of the first optical signal and the polarization state of the second optical signal is greater than or equal to 0 and less than any angle of 90 degrees. If the polarization state of the first optical signal is perpendicular to the polarization state of the second optical signal, the receiving device cannot obtain the beat signal of the first optical signal and the second optical signal.

[0080] In this embodiment, the polarization state of the first optical signal and the polarization state of the second optical signal are the same as an example. The transmitting device may transmit the first optical signal and the second optical signal having the same polarization state to the receiving device. For another example, the receiving device may change the polarization state of the received first optical signal and / or the polarization state of the second optical signal to ensure that the polarization state of the first optical signal and the polarization state of the second optical signal meet the condition that the minimum angle difference is greater than or equal to 0 and less than 90 degrees.

[0081] This embodiment shows that the beat frequency signal is successfully obtained, and the difference between the optical frequency of the first optical signal and the optical frequency of the second optical signal shown in this embodiment is less than or equal to the preset value. This embodiment does not limit the specific value of the preset value. The optical frequency of the first optical signal and the optical frequency of the second optical signal are equal or approximately equal to improve the accuracy of the first delay difference obtained. This embodiment takes the optical frequency of the first optical signal and the optical frequency of the second optical signal as an example.

[0082] The expression of the beat frequency signal shown in this embodiment can refer to the following expression 3:

[0083] Expression 3:

[0084] Among them, E R (t) represents the beat signal. B represents the amplitude of the beat signal. ω c Represents the angular frequency of light. ωc ×(t-τ2) represents the relationship between t-τ2 and ω c The product of . Represents the phase noise of the beat signal as it changes with t-τ1. Represents the phase noise of the beat signal as it changes with (t-τ2).

[0085] It should be noted that the expression 3 shown in this embodiment is an example, not a limitation. In other examples, parameters may be added or reduced, or the coefficients in the current expression 3 may be changed, etc., without specific limitation.

[0086] Step 204: The receiving device samples the beat frequency signal to obtain phases of N sampled signals.

[0087] The phases of the N sampling signals are phases obtained by the receiving device sampling the beat frequency signal at N different sampling moments. In the N sampling moments shown in this embodiment, the time intervals between any two adjacent sampling moments are equal, or, in the N sampling moments, the time intervals between some two adjacent sampling moments are equal.

[0088] The following is an exemplary description of the process of the receiving device obtaining the phase of the i-th sampling signal. Wherein, i is a positive integer greater than or equal to 1 and less than or equal to N. The following expression 4 represents the phase of the i-th sampling signal:

[0089] Expression 4:

[0090] Among them, φ n (i) represents the phase of the i-th sampling signal. T represents the sampling time. iT represents the sampling result of φ n (i) is the i-th sampling time of (i). Let τ be the first delay difference, and τ=τ2-τ1, the first delay difference is the difference between the delay τ1 of the first optical signal transmitted via the first transmission channel and the delay τ2 of the second optical signal transmitted via the second transmission channel. In other examples, τ=τ1-τ2, which is not specifically limited. ω c ×τ represents the relationship between τ and angular frequency ω c The product of . represents the phase noise of the beat signal at the i-th sampling moment. It represents the phase noise of the beat frequency signal as iT-τ changes.

[0091] It should be noted that the expression 4 shown in this embodiment is an example, not a limitation. In other examples, parameters may be added or reduced, or the coefficients in the current expression 4 may be changed, etc., without specific limitation.

[0092] It can be seen that the phases of the N sampling signals obtained by the receiving device are φ n(1)φ n (2)φ n (3)……φ n (N).

[0093] This embodiment does not limit the value of N, and the value of N is positively correlated with the measurement time range of the receiving device. It can be seen that the larger the value of N, the longer the measurement time range. If the first delay difference is within the measurement time range of the receiving device, the receiving device can accurately measure the first delay difference.

[0094] The higher the sampling frequency of the beat frequency signal in this embodiment, the higher the accuracy of the first time delay difference obtained by the receiving device.

[0095] Step 205: The receiving device obtains a first delay difference based on the phases of the N sampling signals.

[0096] Specifically, the receiving device performs Fourier transform on the phases of the N sampling signals to obtain power spectral density (PSD) corresponding to the N sampling signals. This embodiment uses the method of obtaining the PSD corresponding to the phases of the N sampling signals by Fourier transform as an example for illustrative description. In other examples, the receiving device may also obtain the PSD corresponding to the N sampling signals by other means.

[0097] The PSD corresponding to the N sampling signals shown in this embodiment has an envelope with a period of the first delay difference τ. To this end, the receiving device obtains the first delay difference τ in the PSD corresponding to the N sampling signals. Specifically, the receiving device performs Fourier transform on the PSD corresponding to the N sampling signals to obtain the first delay difference τ included in the target period.

[0098] Optionally, the receiving device shown in this embodiment may perform the above steps 201 to 205 multiple times to obtain multiple first delay differences. The receiving device may calculate the average value, median value, weighted average value, etc. of the multiple first delay differences to improve the accuracy of the obtained first delay differences.

[0099] It can be seen that the beat signal shown in this embodiment is obtained by mixing the first optical signal and the second optical signal by the receiving device. Then, the beat signal reflects the correlation between the first optical signal and the second optical signal. The receiving device can successfully obtain the first delay difference based on the beat signal reflecting the correlation between the first optical signal and the second optical signal.

[0100] Moreover, in the process of obtaining the first delay difference, there is no need for the sending device and the receiving device to modulate the timestamp in the optical signal, nor is there a need for the sending device and the receiving device to demodulate the optical signal to obtain the timestamp. It can be seen that the process of obtaining the first delay difference does not need to be supported by the upper layer protocol, which improves the efficiency of obtaining the first delay difference. Moreover, since there is no need for the upper layer protocol to process, the first delay difference obtained in this embodiment does not include the time of the upper layer protocol processing, which effectively improves the accuracy of the first delay difference obtained.

[0101] In the process of obtaining the first time delay difference by the method shown in this embodiment, no other equipment is required. For example, no optical time domain reflectometer (OTDR) is required, which reduces the cost of measuring the first time delay difference. Since obtaining the time delay difference by OTDR requires manual operation, the method shown in this embodiment does not require manual participation, which improves the reliability and accuracy of measuring the first time delay difference.

[0102] Embodiment 2

[0103] The method for obtaining the delay difference provided in this embodiment can effectively improve the accuracy of the first delay difference obtained by the receiving device. Figure 3 As shown in the figure, Figure 3 This is a flowchart of the steps of the second embodiment of the method for obtaining the delay difference provided in the present application.

[0104] Step 301: A receiving device receives a first optical signal from a sending device via a first transmission channel.

[0105] Step 302: The receiving device receives a second optical signal from the sending device via a second transmission channel.

[0106] Step 303: The receiving device performs beat frequency processing on the first optical signal and the second optical signal to obtain a beat frequency signal.

[0107] Step 304: The receiving device samples the beat frequency signal to obtain phases of N sampled signals.

[0108] For the execution process of steps 301 to 304 shown in this embodiment, please refer to steps 201 to 204 shown in the first embodiment, and the details are not repeated here.

[0109] Step 305: The receiving device obtains a differential phase sequence according to the phases of the N sampling signals.

[0110] The following describes the process of the receiving device obtaining the differential phase sequence:

[0111] First, the receiving device obtains a first phase sequence and a second phase sequence from N sampling signals. Specifically, the first phase sequence includes the phases of k sampling signals among the phases of the N sampling signals. The second phase sequence includes the phases of j sampling signals among the phases of the N sampling signals. The values ​​of k and j shown in this embodiment are respectively positive integers greater than 1 and less than N, and k is equal to j. As shown in this embodiment, it is necessary to obtain the first delay difference based on the first phase sequence and the second phase sequence. To this end, the sampling moments of the phases of two sampling signals in the same sequence order in the first phase sequence and the second phase sequence are different, as shown in the following Table 1:

[0112] Table 1

[0113]

[0114] A sequence includes multiple elements arranged in sequence order. A sequence index indicates the sequence order of each element included in the sequence. For example, the element corresponding to sequence index 1 is the first one among the multiple elements in the sequence. The element corresponding to sequence index 2 is the second one among the multiple elements in the sequence, and so on.

[0115] It can be seen that the first phase sequence includes multiple elements arranged in sequence order, such as φ n (a1),φ n (a2),φ n (a3),φ n (Ta4),φ n (a5),φ n (a6)…φ n (k). φ n (a1) represents the phase of the sampling signal obtained at the sampling time Ta1 among the phases of the N sampling signals. n (k) represents the phase of the sampling signal acquired by sampling at the sampling time Tk among the phases of the N sampling signals.

[0116] The second phase sequence includes a plurality of elements arranged in sequence order, such as φ n (b1),φ n (b2),φ n (b3),φ n (b4),φ n (b5),φ n (b6)…φ n (j). φ n (b1) represents the phase of the N sampling signals. The phase of the sampling signal obtained by sampling at the sampling time Tb1. And so on, φ n(j) represents the phase of the sampling signal acquired by sampling at the sampling time Tj among the phases of the N sampling signals.

[0117] In the first phase sequence and the second phase sequence shown in this embodiment, the sampling moments of the phases of the two sampling signals in the same sequence order are different, which means that the sampling moments of the two elements corresponding to the same sequence index in the first phase sequence and the second phase sequence are different. n (a1) and φ n (b1), the corresponding sampling time Ta1 is different from the sampling time Tb1. For example, φ corresponding to sequence index 2 n (a2) and φ n (b2), the corresponding sampling time Ta2 is different from the sampling time Tb2, and so on.

[0118] For better understanding, the following describes how to obtain the first phase sequence and the second phase sequence from N sampling signals in combination with a specific example:

[0119] Example 1

[0120] In this example, the beat frequency signal is sampled at N sampling moments (ie, T1, T2, ..., TN) to obtain the phases of the N sampling signals, ie, φ n (1)φ n (2)φ n (3)……φ n (N). The phases of the k sampling signals included in the first phase sequence are continuously taken in sequence order among the N sampling signal phases. Moreover, the phases of the j sampling signals included in the second phase sequence are continuously taken in sequence order among the N sampling signal phases as an example.

[0121] Specifically, this example takes the value of N as 100 as an example. It can be seen that the receiving device obtains the phases of 100 sampled signals. This example also takes the value of k and the value of j as 90 as an example. Then, the first phase sequence includes the phases of 90 sampled signals, and the first phase sequence includes the phases of 90 consecutive sampled signals among the phases of the 100 sampled signals. For example, the first phase sequence includes φ n (1)φ n (2)φ n (3)……φ n (90). It can be seen that the first phase sequence includes the first 90 phases of the 100 sampling signals.

[0122] Likewise, the second phase sequence includes the phases of 90 sampling signals, and the second phase sequence includes the phases of 90 consecutive sampling signals among the phases of 100 sampling signals.n (11)φ n (12)

[0123] φ n (13)……φ n (100). It can be seen that the second phase sequence includes the last 90 phases of the 100 sampling signals.

[0124] The first phase sequence and the second phase sequence shown in this example can be seen in the following Table 2:

[0125] Table 2

[0126]

[0127] Combining the first phase sequence and the second phase sequence, it can be seen that the sampling moments of the phases of the two sampling signals in the same sequence order are different. That is, in the first phase sequence and the second phase sequence, the sampling moments of the two elements corresponding to the same sequence index are different. For example, φ corresponding to sequence index 1 n (1) and φ n (T1), the corresponding sampling time T1 is different from the sampling time T11.

[0128] It should be noted that this embodiment does not limit the number of phases of the sampling signals included in the first phase sequence and the second phase sequence.

[0129] Example 2

[0130] In this example, the beat frequency signal is sampled at N sampling moments (ie, T1, T2, ..., TN) to obtain the phases of the N sampling signals, ie, φ n (1)φ n (2)φ n (3)……φ n (N). In this example, the phases of the k sampling signals included in the first phase sequence are arranged at intervals among the phases of the N sampling signals. Moreover, the phases of the j sampling signals included in the second phase sequence are arranged at intervals among the phases of the N sampling signals. This example also needs to ensure that the time interval between the sampling moments of the phases of any two adjacent sampling signals in the first phase sequence is equal to the time interval between the sampling moments of the phases of any two adjacent sampling signals in the second phase sequence.

[0131] Specifically, this example takes the value of N as 10, and the value of k and the value of j as 5. Then, the first phase sequence includes the phases of 5 sampling signals, and the first phase sequence includes the phases of the sampling signals arranged as odd numbers among the phases of the 10 sampling signals. For example, the first phase sequence includes {φ n (1)φn (3)φ n (5)……φ n (9)}. It can be seen that the first phase sequence includes 5 phases of the 10 sampling signals, and the phases of any two adjacent sampling signals included in the first phase sequence are separated by 1 sampling period. n (1) and φ n (3) as an example, φ n (1) and φ n (3) Interval φ n (2) is the sampling period, i.e., φ n (1) and φ n (3) There is a total interval of one sampling period.

[0132] Similarly, the second phase sequence includes the phases of 5 sampling signals, and the second phase sequence includes the phases of the sampling signals arranged as even numbers among the phases of the 10 sampling signals. For example, the second phase sequence includes {φ n (2)φ n (4)φ n (6)……φ n (10)}. It can be seen that the second phase sequence includes 5 phases of the 10 sampling signals, and the phases of any two adjacent sampling signals included in the second phase sequence are separated by 1 sampling period. n (2) and φ n (4) as an example, φ n (2) and φ n (4) Interval φ n The sampling period of (3), i.e., φ n (2) and φ n (4) There is a total interval of one sampling period.

[0133] The first phase sequence and the second phase sequence shown in this example can be seen in the following Table 3:

[0134] Table 3

[0135]

[0136] Combining the first phase sequence and the second phase sequence, it can be seen that the sampling moments of the phases of the two sampling signals in the same sequence order are different. That is, in the first phase sequence and the second phase sequence, the sampling moments of the two elements corresponding to the same sequence index are different. For example, φ corresponding to sequence index 1 n (1) and φ n (2) The corresponding sampling time T1 and sampling time T2 are different.

[0137] The following describes how to obtain a differential phase sequence based on the first phase sequence and the second phase sequence that have been obtained:

[0138] The differential phase sequence shown in this embodiment is the difference between the first phase sequence and the second phase sequence. Specifically, the differential phase sequence shown in this embodiment includes K differential phases. The differential phase sequence can be expressed as {Δφ1, Δφ2, Δφ3...Δφ K}. Each differential phase included in the differential phase sequence is the difference between the phases of two sampling signals in the same sequence order in the first phase sequence and the second phase sequence. For example, the kth differential phase included in the differential phase sequence, i.e., Δφ k is the difference between the kth phase included in the first phase sequence and the kth phase included in the second phase sequence, and so on.

[0139] For example, as shown in Example 2 above, if the first phase sequence includes φ n (1)φ n (3)φ n (5)……φ n (9). The second phase sequence includes φ n (2)φ n (4)φ n (6)……φ n (10). Then, the differential phase sequence can be expressed as Δφ n =Δφ1, Δφ2, Δφ3...Δφ5. Among them, Δφ1=φ n (1)-φ n (2), Δφ2=φ n (3)-φ n (4), and so on, Δφ5=φ n (9)-φ n (10).

[0140] In this example, the phases of the multiple sampling signals included in the first phase sequence are sequentially used as subtrahends, and the phases of the multiple sampling signals included in the second phase sequence are sequentially used as minuends to obtain a differential phase sequence, which is not limited. For example, the phases of the multiple sampling signals included in the second phase sequence can also be used as subtrahends, and the phases of the multiple sampling signals included in the first phase sequence can be used as minuends to obtain a differential phase sequence, which is not limited in this embodiment.

[0141] This embodiment takes the phases of the multiple sampling signals included in the first phase sequence as subtrahends in sequence, and the phases of the multiple sampling signals included in the second phase sequence as minuends in sequence as an example. In other examples, the phases of the multiple sampling signals included in the first phase sequence can be randomly used as subtrahends, and the phases of the multiple sampling signals included in the second phase sequence can be randomly used as minuends as an example, as long as it can be ensured that different differential phases are based on different phases from the first phase sequence and the second phase sequence. For example, Δφ1=φ n (1)-φ n (4), Δφ2=φ n (5)-φ n (10) etc.

[0142] To obtain Δφ i As an example, how the receiving device obtains the differential phase sequence, the Δφ i is any differential phase included in the differential phase sequence, Δφ i =φ n (i)-φ n (i+1).

[0143] in,

[0144] It can be seen that

[0145] Step 306: The receiving device obtains a first delay difference based on the differential phase sequence.

[0146] Specifically, the receiving device performs Fourier transform on the differential phase sequence to obtain the power spectral density (PSD) of the differential phase sequence. This embodiment is illustrative by taking the method of obtaining the PSD of the differential phase sequence by Fourier transform as an example. In other examples, the receiving device may also obtain the PSD of the differential phase sequence by other means. For example, the differential phase sequence is correlated with sinusoidal signals of different frequencies to obtain the PSD.

[0147] For example, the PSD of the differential phase sequence acquired by the receiving device can be shown in Expression 5 as shown below:

[0148] Expression 5:

[0149] in, Theoretically, it is a constant, and f is the baseband frequency of the optical signal output by the laser of the transmitting device. i] has an envelope with a period of the first time delay difference τ. The receiving device obtains the first time delay difference τ in the PSD of the differential phase sequence. Specifically, the receiving device performs Fourier transform on the PSD of the differential phase sequence to obtain the first time delay difference τ included in the target period.

[0150] Optionally, the receiving device shown in this embodiment may perform the above steps 301 to 306 multiple times to obtain multiple first delay differences. The receiving device may calculate the average value, median value, weighted average value, etc. of the multiple first delay differences to improve the accuracy of the obtained first delay differences.

[0151] It can be seen that the beat signal shown in this embodiment is obtained by mixing the first optical signal and the second optical signal by the receiving device. Then, the beat signal reflects the correlation between the first optical signal and the second optical signal. The receiving device obtains a differential phase sequence based on the phases of N sampling signals. The receiving device obtains the first delay difference based on the differential phase sequence, which can improve the accuracy of obtaining the first delay difference.

[0152] This embodiment shows that the accuracy of the measured first time delay difference can be adjusted. As shown above, the receiving device can change the measurement range of the first time delay difference that can be measured by changing the value of N in the phase of the N sampling signals obtained by sampling. For example, the larger the value of N, the longer the duration of the first time delay difference that can be measured by the receiving device. Moreover, if the receiving device needs to improve the accuracy of the first time delay difference obtained, the receiving device can increase the sampling frequency of sampling the beat frequency signal.

[0153] Embodiment 3

[0154] The method for obtaining the delay difference provided in this embodiment is different from that in the first embodiment in that, in the first embodiment, the receiving device can only obtain the first delay difference, and the receiving device cannot determine which optical signal, transmitted via the first transmission channel or the optical signal, is the first to arrive at the receiving device. The method provided in this embodiment can obtain the first delay difference and can also determine which optical signal, transmitted via the first transmission channel or the optical signal, is the first to arrive at the receiving device. Figure 4A As shown in the figure, Figure 4A This is a flowchart of the steps of the third embodiment of the method for obtaining the delay difference provided in the present application.

[0155] Step 401: A receiving device receives a first optical signal from a sending device via a first transmission channel.

[0156] Step 402: The receiving device receives a second optical signal from the sending device via a second transmission channel.

[0157] Step 403: The receiving device performs beat frequency processing on the first optical signal and the second optical signal to obtain a beat frequency signal.

[0158] Step 404: The receiving device samples the beat frequency signal to obtain phases of N sampled signals.

[0159] Step 405: The receiving device obtains a differential phase sequence according to the phases of the N sampling signals.

[0160] Step 406: The receiving device obtains a first delay difference based on the differential phase sequence.

[0161] For the execution process of steps 401 to 406 shown in this embodiment, please refer to steps 301 to 306 shown in the second embodiment, and the details are not repeated here.

[0162] Step 407: The receiving device receives the third optical signal from the sending device via the third transmission channel.

[0163] This step can be seen in Figure 4B As shown. Among them, Figure 4B This is an example diagram of the first application scenario of the method for obtaining the delay difference provided in the present application. Specifically, after the receiving device successfully obtains the first delay difference through the above steps 401 to 406, an optical device 423 is added to the first transmission channel 111 to form a third transmission channel. It can be seen that the difference between the third transmission channel and the first transmission channel is that the third transmission channel has an optical device 423 added relative to the first transmission channel. In this application scenario, the third transmission channel includes a first sub-transmission channel 421 and a second sub-transmission channel 422. The optical splitter module 102, the first sub-transmission channel 421, the optical device 423, the second sub-transmission channel 422 and the receiving device 103 are connected in sequence. For a detailed description of the sending device 101, the transmission channel 110, the first transmission channel, the second transmission channel 112 and the receiving device 103, please refer to Figure 1 As shown, the details are not repeated here.

[0164] The optical device 423 shown in this embodiment may be an optical waveguide device. For another example, the optical device 423 may be a circulator, etc., and the specific type is not limited in this embodiment. The optical device 423 can ensure that the first delay is less than the second delay. Among them, the first delay is the delay of the first optical signal transmitted via the first transmission channel, and the second delay is the delay of the third optical signal transmitted via the third transmission channel. The first optical signal and the third optical signal shown in this embodiment are from the same sending device 101. Specifically, the moment when the sending device 101 outputs the first optical signal is earlier than the moment when the sending device 101 outputs the third optical signal.

[0165] Step 408: The receiving device receives the fourth optical signal from the sending device via the second transmission channel.

[0166] The third optical signal and the fourth optical signal shown in this embodiment are both from two identical optical signals after being split by the splitting module 102. For the description of the specific process of the splitting module splitting the third optical signal and the fourth optical signal, please refer to the description of the specific process of the splitting module splitting the first optical signal and the second optical signal shown in the first embodiment, which will not be described in detail.

[0167] Step 409: The receiving device obtains the second delay difference.

[0168] The second delay difference shown in this embodiment is the difference between the second delay and the third delay. The third delay is the delay of the fourth optical signal being transmitted via the second transmission channel. The process of the receiving device obtaining the second delay difference according to the third optical signal and the fourth optical signal shown in this embodiment can be referred to as shown in steps 401 to 406, and the process of the receiving device obtaining the first delay difference according to the first optical signal and the second optical signal is not described in detail.

[0169] Step 410: If the receiving device determines that the second delay difference is greater than the first delay difference, it determines that the transmission delay of the first transmission channel is less than the transmission delay of the second transmission channel.

[0170] In this embodiment, when the receiving device determines that the second delay difference is greater than the first delay difference, the receiving device determines that the transmission delay of the first transmission channel is less than the transmission delay of the second transmission channel. The transmission delay of the first transmission channel refers to the delay of the optical signal transmitted through the first output channel. Figure 1 As shown, the start time of the transmission delay of the first transmission channel is the time when the first optical signal is output by the optical splitting module 102 to enter the first transmission channel 111, and the end time of the transmission delay of the first transmission channel is the time when the first optical signal is output by the first transmission channel 111 to enter the receiving device 103. Figure 4B As shown, the transmission delay of the third transmission channel starts at the moment when the third optical signal is output by the optical splitting module 102 to enter the first sub-transmission channel 421. The end time of the transmission delay of the third transmission channel is the moment when the third optical signal is output by the second sub-transmission channel 422 to enter the receiving device 103.

[0171] It can be seen that when the second delay difference is greater than the first delay difference, for two optical signals of the same source, the time when the optical signal transmitted via the first transmission channel arrives at the receiving device is earlier than the time when the optical signal transmitted via the second transmission channel arrives at the receiving device.

[0172] Step 411: If the receiving device determines that the second delay difference is less than or equal to the first delay difference, it determines that the transmission delay of the first transmission channel is greater than the transmission delay of the second transmission channel.

[0173] For the description of the transmission delay of the first transmission channel and the description of the transmission delay of the second transmission channel, please refer to step 311, and the specific details are not repeated. It can be seen that when the second delay difference is less than the first delay difference, the time when the optical signal of the same source two optical signals transmitted via the first transmission channel reaches the receiving device is later than the time when the optical signal transmitted via the second transmission channel reaches the receiving device.

[0174] For a description of the beneficial effect of the receiving device being able to determine the first delay difference by using the method shown in this embodiment, please refer to the description in the first embodiment, which will not be described in detail. The method described in this embodiment can also obtain the size relationship between the transmission delay of the first transmission channel and the transmission delay of the second transmission channel, and then determine which of the optical signals transmitted via the first transmission channel and the optical signals transmitted via the second transmission channel will arrive at the receiving device first when the sending device sends two optical signals of the same source to the receiving device. In order to obtain the transmission status of the optical signal transmitted between the sending device and the receiving device. And improve the accuracy of the delay compensation of the first transmission channel and the second transmission channel.

[0175] Embodiment 4

[0176] The method provided in this embodiment can achieve the purpose of measuring the delay of an optical device. The delay of an optical device refers to the delay during which an optical signal is transmitted from an input port of the optical device to the optical device and then output through an output port of the optical device. Figure 5 As shown in the figure, Figure 5 This is a flowchart of the steps of the fourth embodiment of the method for obtaining the delay difference provided in the present application.

[0177] Step 501: A receiving device receives a first optical signal from a sending device via a first transmission channel.

[0178] Step 502: The receiving device receives a second optical signal from the sending device via a second transmission channel.

[0179] Step 503: The receiving device performs beat frequency processing on the first optical signal and the second optical signal to obtain a beat frequency signal.

[0180] Step 504: The receiving device samples the beat frequency signal to obtain phases of N sampled signals.

[0181] Step 505: The receiving device obtains a differential phase sequence according to the phases of the N sampling signals.

[0182] Step 506: The receiving device obtains a first delay difference based on the differential phase sequence.

[0183] For the execution process of steps 501 to 506 shown in this embodiment, please refer to steps 301 to 306 shown in the second embodiment, and the details are not repeated here.

[0184] Step 507: The receiving device receives the third optical signal from the sending device via the third transmission channel.

[0185] Step 508: The receiving device receives the fourth optical signal from the sending device via the second transmission channel.

[0186] In this embodiment, in order to measure the time delay of the optical device, the optical device to be measured can be set in the first transmission channel to achieve the purpose of measuring the optical device. Figure 4B As shown, Figure 4B For the description of the measurement system shown, please refer to the second embodiment and will not be described in detail.

[0187] The method of arranging the optical device in the first transmission channel shown in this embodiment can also be seen in Figure 6 As shown. Among them, Figure 6 This is an example diagram of a second application scenario of the method for obtaining the delay difference provided in this application. The measurement system shown in this embodiment includes a transmitting device 601, a splitter module 602, a deflection module 605, an optical device 604, and a reflection module 606 connected in sequence. The measurement system also includes a receiving device 603 connected to the deflection module 605. For a detailed description of the transmitting device 601, the splitter module 602, the optical device 604, and the receiving device 603, see Figure 4B The relevant instructions shown are not repeated in detail.

[0188] Specifically, after the receiving device 603 has successfully obtained the first delay difference, the deflection module 605, the optical device 604 and the reflection module 606 can be connected to the measurement system through the third transmission channel. The third transmission channel shown in this embodiment may include a first sub-channel 611, a second sub-channel 612, a third sub-channel 613 and a fourth sub-channel 614. One end of the first sub-channel 611 is connected to the output port of the light splitting module 602. The other end of the first sub-channel 611 is connected to the first port of the deflection module 605. One end of the second sub-channel 612 is connected to the second port of the deflection module. The other end of the second sub-channel 612 is connected to the third port of the optical device 604. One end of the third sub-channel 613 is connected to the fourth port of the optical device 604. The other end of the third sub-channel 613 is connected to the reflection module 606. One end of the fourth sub-channel 614 is connected to the fifth port of the deflection module 605. The other end of the fourth sub-channel 614 is connected to the receiving device 603.

[0189] It can be known that, in order to achieve the purpose of measuring the time delay of the optical device 604, the deflection module 605, the optical device 604, and the reflection module 606 can be connected in the measurement system through the third transmission channel. The following describes the process of the receiving device receiving the third optical signal through the third transmission channel and the receiving device receiving the fourth optical signal through the second transmission channel:

[0190] The third optical signal and the fourth optical signal shown in this embodiment are both from two optical signals of the same source after being split by the splitting module 602. For the description of the specific process of the splitting module 602 splitting the third optical signal and the fourth optical signal, please refer to the description of the specific process of the splitting module splitting the first optical signal and the second optical signal shown in the first embodiment, and the details are not repeated here.

[0191] like Figure 6 As shown, the fourth optical signal from the optical splitting module 602 is transmitted to the receiving device 603 via the second transmission channel 620 .

[0192] The third optical signal from the optical splitter module 602 is transmitted to the deflection module 605 via the first sub-channel 611. The deflection module 605 receives the third optical signal transmitted via the first sub-channel 611 through the first port. The deflection module 605 shown in this embodiment is used to change the transmission direction of the third optical signal to ensure that the third optical signal passing through the optical device 604 can be transmitted to the receiving device. This embodiment is exemplified by taking the deflection module 605 as an optical circulator as an example. The third optical signal input to the first port of the deflection module 605 is output through the second port of the deflection module 605. The third optical signal output from the second port of the deflection module 605 is transmitted to the third port of the optical device 604 via the second sub-channel 612. After passing through the optical device 604, the third optical signal is output through the fourth port of the optical device 604. The third optical signal output from the fourth port of the optical device 604 is transmitted to the reflection module 606 via the third sub-channel 613. The reflection module 606 is used to reflect the third optical signal, so as to reflect the reflected third optical signal back to the fourth port of the optical device 604 via the third sub-channel 613. The present embodiment does not limit the specific type of the reflection module 606, as long as the reflection module 606 can reflect the third optical signal, for example, the reflection module 606 can be a reflector made of a metal material. For another example, the reflection module 606 can be a grating with a reflection function, etc., which is not specifically limited in the present embodiment.

[0193] The third optical signal input through the fourth port of the optical device 604 and the third optical signal output through the third port of the optical device 604 are transmitted to the second port of the deflection module 605 via the second sub-channel 612. The fifth port of the deflection module 605 outputs the third optical signal from the second port of the deflection module 605. The third optical signal output from the second port of the deflection module 605 is transmitted to the receiving device via the second sub-channel 614.

[0194] In the measurement system shown in this embodiment, in order to facilitate the measurement of the delay of the optical device 604 to be measured, the sending device and the receiving device shown in this embodiment can be set in the same device. Figure 7 As shown, Figure 7 This is an example diagram of the third application scenario of the method for obtaining the delay difference provided by this application. It can be seen that, Figure 7 The measurement system shown includes a transceiver device 700, and the transceiver device 700 includes a sending module 701 and a receiving module 702. For a description of the sending module 701 and the receiving module 702, see Figure 6 The description of the sending device and the receiving device shown in the figure will not be repeated in detail. It can be seen that when the delay of the optical device 604 needs to be measured, it can be done by Figure 7 In the manner shown, the transceiver device 700 is connected to the optical device 604. For a detailed description of the connection method, see Figure 6 As shown, no further elaboration is given.

[0195] Optionally, the optical splitter module 602 described in this embodiment may also be disposed in the transceiver device 700, so that the transceiver module 700 directly outputs the optical signals shown above, which is not specifically limited.

[0196] Step 509: The receiving device obtains the second delay difference.

[0197] For the execution process of step 509 shown in this embodiment, please refer to step 309 of the second embodiment, and the details are not repeated here.

[0198] Step 510: The receiving device determines the delay of the optical device as the absolute value of the difference between the first delay difference and the second delay difference.

[0199] When the receiving device obtains the first delay difference and the second delay difference, the receiving device determines the delay of the optical device as the absolute value of the difference between the first delay difference and the second delay difference. It can be seen that the delay of the optical device = |first delay difference-second delay difference|.

[0200] It can be seen that by adopting the method shown in this embodiment, when it is necessary to measure the delay of an optical device, the optical device can be connected to a measurement system, so as to obtain the delay of the optical device based on the first delay difference and the second delay difference. In the process of measuring the delay of the optical device, there is no need to use equipment such as OTDR, which reduces the cost of measuring the delay of the optical device. Moreover, in the process of obtaining the first delay difference and the second delay difference, there is no need for the sending device to modulate the timestamp in each optical signal, and there is no need for the receiving device to demodulate and process each optical signal from the sending device to obtain the timestamp. In the process of obtaining the first delay difference and the second delay difference, there is no need to obtain the support of the upper layer protocol, which improves the accuracy of obtaining the delay of the optical device.

[0201] Embodiment 5

[0202] The method provided in this embodiment can measure the length difference between the length of the first transmission channel and the length of the second transmission channel. Figure 8 As shown in the figure, Figure 8 This is a flowchart of the steps of the fifth embodiment of the method for obtaining the delay difference provided in the present application.

[0203] Step 801: A receiving device receives a first optical signal from a sending device via a first transmission channel.

[0204] Step 802: The receiving device receives a second optical signal from the sending device via a second transmission channel.

[0205] Step 803: The receiving device performs beat frequency processing on the first optical signal and the second optical signal to obtain a beat frequency signal.

[0206] Step 804: The receiving device samples the beat frequency signal to obtain phases of N sampled signals.

[0207] Step 805: The receiving device obtains a differential phase sequence according to the phases of the N sampling signals.

[0208] Step 806: The receiving device obtains a first delay difference based on the differential phase sequence.

[0209] For the execution process of steps 801 to 806 shown in this embodiment, please refer to steps 301 to 306 shown in the second embodiment, and the details are not repeated here.

[0210] Step 807: The receiving device obtains a target length difference according to the first delay difference.

[0211] The target length difference shown in this embodiment is the difference between the length of the first transmission channel and the length of the second transmission channel. Specifically, the receiving device obtains the target length difference according to the following formula:

[0212] Wherein, ΔL is the target length difference, c is the speed of light, Δt is the first delay difference, and n is the target refractive index. The refractive index of the first transmission channel shown in this embodiment is equal to the refractive index of the second transmission channel, and both are the target refractive index.

[0213] It can be seen that the method shown in this embodiment can be used to obtain the target length difference between the length of the first transmission channel and the length of the second transmission channel based on the first delay difference between the first transmission channel and the second transmission channel, so as to determine the actual networking situation between the sending device and the receiving device, obtain the link status, and improve the consistency of evaluating the transmission channel length between the first transmission channel and the second transmission channel.

[0214] Embodiment 6

[0215] This embodiment describes the structure of the receiving device from the perspective of functional modules. Fig. 9 As shown. Among them, Fig. 9 This is a structural example diagram of the first embodiment of the receiving device provided in this application. The receiving device shown in this embodiment specifically includes:

[0216] The receiving device 900 includes a receiving module 901 and a processing module 902 connected to the receiving module 901 .

[0217] The receiving module 901 is used to execute the functions related to receiving in any one of the first to fourth embodiments. The processing module 902 is used to execute the functions related to processing in any one of the first to fourth embodiments.

[0218] For example, if the receiving device 900 shown in this embodiment is used to execute the method shown in the first embodiment, the receiving unit 901 is used to execute steps 201 to 202. The processing unit 902 is used to execute steps 203 to 205.

[0219] For example, if the receiving device 900 shown in this embodiment is used to execute the method shown in the second embodiment, the receiving unit 901 is used to execute steps 301 to 302. The processing unit 902 is used to execute steps 303 to 306.

[0220] For another example, if the receiving device 900 shown in this embodiment is used to execute the method shown in Embodiment 3, the receiving unit 901 is used to execute steps 401, 402, 407, and 408. The processing unit 902 is used to execute steps 403 to 406, and to execute steps 409 to 411.

[0221] For another example, if the receiving device 900 shown in this embodiment is used to execute the method shown in Embodiment 4, the receiving unit 901 is used to execute steps 501, 502, 507, and 508. The processing unit 902 is used to execute steps 503 to 506, and the processing unit 902 is also used to execute steps 509 to 510.

[0222] For another example, if the receiving device 900 described in this embodiment is used to execute the method shown in the fifth embodiment, the receiving unit 901 is used to execute steps 801 and 802. The processing unit 902 is used to execute steps 803 to 807.

[0223] Embodiment 7

[0224] This embodiment describes the structure of the receiving device from the perspective of physical hardware. Fig.10 As shown. Among them, Fig.10 This is a diagram showing a second embodiment of the structure of a receiving device provided in this application. The receiving device shown in this embodiment specifically includes:

[0225] The receiving device 1000 shown in this embodiment may include a mixing module 1001 , a trans-impedance amplifier (TIA) 1002 , an analog-to-digital converter (ADC) 1003 , and a processor 1004 , which are connected in sequence.

[0226] Among them, the mixing module 1001 is connected to the first transmission channel and the second transmission channel respectively. For the specific description of the first transmission channel and the second transmission channel, please refer to any of the above embodiments, and no further details are given. The mixing module 1001 can receive a first optical signal from the first transmission channel and a second optical signal from the second transmission channel. The mixing module 1001 is also used to obtain a beat signal of the first optical signal and the second optical signal. For the description of the specific process of obtaining the beat signal, please refer to any of the above embodiments, and no further details are given.

[0227] In this embodiment, the frequency mixing module 1001 includes a frequency mixing unit and a photoelectric conversion unit. The specific implementation of the frequency mixing module 1001 is not limited. For example, the frequency mixing unit of the frequency mixing module 1001 can be a 90-degree mixer, a 180-degree mixer, or a combination of several mixers. The photoelectric conversion unit can be a photodiode (PD), an avalanche photodiode (APD), etc., which are not specifically limited.

[0228] The TIA 1002 is used to convert the beat frequency signal from the mixing module 1001 into an amplified beat frequency signal. The ADC 1003 is used to perform analog-to-digital conversion on the amplified beat frequency signal to obtain the converted beat frequency signal. Optionally, the receiving device 1000 shown in this embodiment may not include the TIA 1002, and the ADC 1003 directly processes the beat frequency signal from the mixing module 1001.

[0229] The processor 1004 is used to obtain the first delay difference according to the beat frequency signal. The specific acquisition process can be referred to any of the above embodiments, and will not be described in detail.

[0230] The form of the processor 1004 shown in this embodiment is not limited. For example, the processor 1004 may be one or more chips, or one or more integrated circuits. For example, the processor 1004 may be one or more field-programmable gate arrays (FPGA), digital signal processors (DSP), application specific integrated circuits (ASIC), system on chip (SoC), central processor unit (CPU), network processor (NP), microcontroller unit (MCU), programmable logic device (PLD) or other integrated chips, or any combination of the above chips or processors, etc., which will not be described in detail.

[0231] The receiving device 1000 shown in this embodiment may further include a memory connected to the processor 1004, and the memory stores program codes. The processor 1004 calls the program codes in the memory to execute the processing functions performed by the processor 1004 shown in this embodiment.

[0232] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for obtaining a delay difference, characterized in that: The method comprises: The receiving device receives the first optical signal from the sending device via the first transmission channel; The receiving device receives a second optical signal from the sending device via a second transmission channel, wherein the first transmission channel and the second transmission channel are connected between the sending device and the receiving device respectively; The receiving device samples the beat frequency signals of the first optical signal and the second optical signal to obtain phases of N sampled signals, wherein the phases of the N sampled signals are phases obtained by sampling the beat frequency signals at N different sampling times, respectively, and N is a positive integer greater than 1; The receiving device obtains a first delay difference based on the phases of the N sampling signals, where the first delay difference is a difference between a delay of the first optical signal being transmitted via the first transmission channel and a delay of the second optical signal being transmitted via the second transmission channel.

2. The method according to claim 1, characterized in that The receiving device acquires a first delay difference based on the phases of the N sampling signals, including: The receiving device determines that the difference between the first phase sequence and the second phase sequence is a differential phase sequence, wherein the first phase sequence includes the phases of k sampling signals among the N sampling signals, the second phase sequence includes the phases of j sampling signals among the N sampling signals, k is equal to j, and in the first phase sequence and the second phase sequence, the sampling moments of the phases of two sampling signals in the same sequence order are different; The receiving device acquires the first time delay difference according to the differential phase sequence.

3. The method according to claim 2, characterized in that The time interval between sampling moments of the phases of any two adjacent sampling signals in the first phase sequence is equal to the time interval between sampling moments of the phases of any two adjacent sampling signals in the second phase sequence.

4. The method according to claim 2 or 3, characterized in that: The receiving device acquires the first time delay difference according to the differential phase sequence, including: The receiving device performs Fourier transform on the differential phase sequence to obtain a power spectrum density PSD of the differential phase sequence; The receiving device obtains the first time delay difference from the PSD of the differential phase sequence.

5. The method according to claim 4, characterized in that The receiving device obtains the first time delay difference from the PSD of the differential phase sequence, including: The receiving device performs Fourier transform on the PSD of the differential phase sequence to obtain the first time delay difference.

6. The method according to any one of claims 1 to 3, characterized in that: After the receiving device acquires the first delay difference based on the phases of the N sampling signals, the receiving device further includes: The receiving device receives a third optical signal from the sending device via a third transmission channel, wherein the third transmission channel includes an optical device; The receiving device receives a fourth optical signal from the sending device via the second transmission channel; The receiving device acquires a second delay difference, where the second delay difference is a difference between a delay of the third optical signal being transmitted via the third transmission channel and a delay of the fourth optical signal being transmitted via the fourth transmission channel; If the second delay difference is greater than the first delay difference, the receiving device determines that the transmission delay of the first transmission channel is less than the transmission delay of the second transmission channel.

7. The method according to claim 6, characterized in that After the receiving device obtains the second delay difference, the method further includes: The receiving device determines the delay of the optical device as an absolute value of a difference between the first delay difference and the second delay difference.

8. A receiving device, characterized in that: The receiving device comprises a receiving module and a processing module connected to the receiving module; The receiving module is used to receive a first optical signal from a sending device via a first transmission channel; The receiving module is further used to receive a second optical signal from the sending device via a second transmission channel, wherein the first transmission channel and the second transmission channel are respectively connected between the sending device and the receiving device; The processing module is used to sample the beat frequency signal of the first optical signal and the second optical signal to obtain phases of N sampled signals, wherein the phases of the N sampled signals are phases obtained by sampling the beat frequency signal at N different sampling times, respectively, and N is a positive integer greater than 1; The processing module is further used to obtain a first delay difference based on the phases of the N sampling signals, where the first delay difference is a difference between a delay of the first optical signal being transmitted via the first transmission channel and a delay of the second optical signal being transmitted via the second transmission channel.

9. The receiving device according to claim 8, characterized in that In the process of obtaining the first delay difference based on the phases of the N sampling signals, the processing module is specifically used to: Determine that the difference between the first phase sequence and the second phase sequence is a differential phase sequence, wherein the first phase sequence includes the phases of k sampling signals among the N sampling signals, the second phase sequence includes the phases of j sampling signals among the N sampling signals, k is equal to j, and in the first phase sequence and the second phase sequence, the sampling moments of the phases of two sampling signals in the same sequence order are different; The first time delay difference is acquired according to the differential phase sequence.

10. The receiving device according to claim 9, characterized in that The time interval between sampling moments of the phases of any two adjacent sampling signals in the first phase sequence is equal to the time interval between sampling moments of the phases of any two adjacent sampling signals in the second phase sequence.

11. The receiving device according to claim 9 or 10, characterized in that: The processing module is specifically used in the process of acquiring the first time delay difference according to the differential phase sequence: Performing Fourier transform on the differential phase sequence to obtain a power spectrum density PSD of the differential phase sequence; The first time delay difference is obtained from the PSD of the differential phase sequence.

12. The receiving device according to claim 11, characterized in that The process in which the processing module obtains the first time delay difference from the PSD of the differential phase sequence is specifically used to: Perform Fourier transform on the PSD of the differential phase sequence to obtain the first time delay difference.

13. The receiving device according to any one of claims 8 to 10, characterized in that: The processing module is also used for: receiving a third optical signal from the transmitting device via a third transmission channel, wherein the third transmission channel includes an optical device; receiving a fourth optical signal from the sending device via the second transmission channel; Obtaining a second delay difference, where the second delay difference is a difference between a delay of transmitting the third optical signal via the third transmission channel and a delay of transmitting the fourth optical signal via the fourth transmission channel; If the second delay difference is greater than the first delay difference, it is determined that the transmission delay of the first transmission channel is less than the transmission delay of the second transmission channel.

14. The receiving device according to claim 13, characterized in that The processing module is also used for: The delay of the optical device is determined as an absolute value of a difference between the first delay difference and the second delay difference.

15. A measurement system, characterized in that: The measurement system includes a transmitting device and a receiving device, and also includes a first transmission channel and a second transmission channel connected between the transmitting device and the receiving device; The receiving device is used to receive a first optical signal from a sending device via a first transmission channel; The receiving device is further configured to receive a second optical signal from the sending device via a second transmission channel, wherein the first transmission channel and the second transmission channel are respectively connected between the sending device and the receiving device; The receiving device is further used to sample the beat frequency signals of the first optical signal and the second optical signal to obtain phases of N sampled signals, wherein the phases of the N sampled signals are phases obtained by sampling the beat frequency signals at N different sampling times, respectively, and N is a positive integer greater than 1; The receiving device is further used to obtain a first delay difference based on the phases of the N sampling signals, where the first delay difference is a difference between a delay of the first optical signal being transmitted via the first transmission channel and a delay of the second optical signal being transmitted via the second transmission channel.

16. The measuring system according to claim 15, characterized in that The measurement system further includes a spectroscopic module, which is connected to the sending device and is also connected to the first transmission channel and the second transmission channel respectively, and is used for: receiving an optical signal from the transmitting device; Splitting the optical signal to obtain the first optical signal and the second optical signal; transmitting the first optical signal to the first transmission channel; The second optical signal is transmitted to the second transmission channel.

17. The measuring system according to claim 15 or 16, characterized in that The receiving device, in the process of acquiring the first delay difference based on the phases of the N sampling signals, is specifically used to: Determine that the difference between the first phase sequence and the second phase sequence is a differential phase sequence, wherein the first phase sequence includes the phases of k sampling signals among the N sampling signals, the second phase sequence includes the phases of j sampling signals among the N sampling signals, k is equal to j, and in the first phase sequence and the second phase sequence, the sampling moments of the phases of two sampling signals in the same sequence order are different; The first time delay difference is acquired according to the differential phase sequence.

18. The measuring system according to claim 17, characterized in that The time interval between sampling moments of the phases of any two adjacent sampling signals in the first phase sequence is equal to the time interval between sampling moments of the phases of any two adjacent sampling signals in the second phase sequence.

19. The measuring system according to claim 17, characterized in that The process in which the receiving device acquires the first time delay difference according to the differential phase sequence is specifically used to: Performing Fourier transform on the differential phase sequence to obtain a power spectrum density PSD of the differential phase sequence; The first time delay difference is obtained from the PSD of the differential phase sequence.

20. The measuring system according to claim 19, characterized in that The process in which the receiving device obtains the first time delay difference from the PSD of the differential phase sequence is specifically used to: Perform Fourier transform on the PSD of the differential phase sequence to obtain the first time delay difference.

21. The measuring system according to any one of claims 15 to 16, characterized in that: The measurement system further includes a third transmission channel, the third transmission channel includes an optical device, and the receiving device is further used for: receiving a third optical signal from the sending device via the third transmission channel; receiving a fourth optical signal from the sending device via the second transmission channel; Obtaining a second delay difference, where the second delay difference is a difference between a delay of transmitting the third optical signal via the third transmission channel and a delay of transmitting the fourth optical signal via the fourth transmission channel; If the second delay difference is greater than the first delay difference, it is determined that the transmission delay of the first transmission channel is less than the transmission delay of the second transmission channel.

22. The measuring system according to claim 21, characterized in that The measurement system further includes a reflection module and a deflection module, wherein the deflection module is connected between the optical device and the receiving device, and the optical device is connected to the reflection module; The first port of the deflection module is used to receive the third optical signal from the sending device; The second port of the deflection module is used to transmit the third optical signal to the third port of the optical device; The fourth port of the optical device is used to transmit the third optical signal to the reflection module; The reflection module is used to reflect the third optical signal to transmit the third optical signal to the fourth port of the optical device; The third port of the optical device is used to transmit the third optical signal to the second port of the deflection module; The fifth port of the deflection module is used to transmit the third optical signal to the receiving device.

23. The measuring system according to claim 21, characterized in that The receiving device is also used for: The delay of the optical device is determined as an absolute value of a difference between the first delay difference and the second delay difference.

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