Optical fiber detection device, optical line terminal and method of identifying an event

Abstract

This application discloses an optical fiber detection device, an optical line terminal, and a method for identifying events, belonging to the field of optical communication technology. In the optical fiber detection device, a light source outputs an optical signal to a modulation module. An encoded pulse generation module outputs encoded pulses to the modulation module. The modulation module performs phase modulation and intensity modulation on optical signal segments within different time periods of the optical signal according to the encoded pulses, obtaining and outputting optical pulse signals to the optical fiber, causing the optical fiber to output a return signal. The light source also outputs an optical signal to a photodetector module. The photodetector module acquires and outputs an electrical signal to a processing module based on the optical signal and the return signal. The electrical signal includes electrical signal segments within different time periods corresponding to the optical signal segments. The processing module performs phase demodulation and intensity demodulation on the electrical signal segments within different time periods, obtaining an event signal used to identify events occurring in the optical fiber. This application can achieve accurate event identification, covering various event identification scenarios.

Description

Technical Field

[0001] This application relates to the field of optical communication technology, and in particular to optical fiber detection devices, optical line terminals, and methods for identifying events. Background Technology

[0002] With the continuous development of optical communication technology, the application of optical fibers is becoming increasingly widespread. By inspecting optical fibers, events occurring in the fibers can be identified, facilitating maintenance based on these events and ensuring the normal operation of the optical fibers.

[0003] During fiber optic testing, the testing device sends coded pulse signals into the fiber. These signals propagate within the fiber and, after scattering or reflection from the fiber's inner walls, generate return signals. The testing device receives these return signals, demodulates them to obtain event signals, and identifies events occurring in the fiber, such as fiber bending or breakage. Higher power in both the return and event signals indicates a strong event, while lower power indicates a weak event.

[0004] In related technology one, the coded pulse signal is obtained through phase modulation, and phase demodulation is required when demodulating the returned signal. However, phase demodulation is easily affected by noise, and the degree of noise influence is more severe when the power of the returned signal is low, resulting in lower accuracy in identifying weak events and very weak events. A very weak event refers to an event where both adjacent events are weak events.

[0005] In related technology two, the coded pulse signal is obtained through intensity modulation, and intensity demodulation is required when demodulating the returned signal. Compared to phase demodulation, intensity demodulation tends to result in lower sidelobe suppression of the event signal, causing confusion between adjacent events. This confusion is more severe when adjacent events include both strong and weak events, leading to lower accuracy in identifying strong-weak or weak-strong events. Strong-weak events refer to adjacent events consisting of a strong event followed by a weak event, and weak-strong events refer to adjacent events consisting of a weak event followed by a strong event.

[0006] It is evident that both related technology one and related technology two suffer from low accuracy in event identification and have certain limitations. Summary of the Invention

[0007] This application provides an optical fiber detection device, an optical line terminal, and a method for identifying events, to accurately detect optical fibers and accurately identify events occurring in the optical fibers. The technical solution provided by this application includes the following aspects.

[0008] In a first aspect, an optical fiber detection device is provided, which includes a light source, an encoded pulse generation module, a modulation module, a photoelectric detection module, and a processing module. The light source and the encoded pulse generation module are respectively connected to the modulation module, the light source and the processing module are respectively connected to the photoelectric detection module, and the modulation module and the photoelectric detection module are also respectively connected to an optical fiber.

[0009] The light source outputs optical signals to the modulation module, which include optical signal segments within different time periods. The encoded pulse generation module outputs encoded pulses to the modulation module. The modulation module performs phase modulation and intensity modulation on the optical signal segments within different time periods according to the encoded pulses, obtaining optical pulse signals, and outputs these signals to the optical fiber, causing the fiber to output a return signal. The light source also outputs optical signals to the photodetector module. The photodetector module acquires electrical signals based on the optical and return signals, and outputs these electrical signals to the processing module. These electrical signals include electrical signal segments within different time periods, corresponding to the optical signal segments. The processing module performs phase demodulation and intensity demodulation on the electrical signal segments within different time periods, obtaining event signals, which are used to identify events occurring in the optical fiber.

[0010] The fiber optic detection device provided in this application performs both phase modulation and corresponding phase demodulation, as well as intensity modulation and corresponding intensity demodulation. The accuracy of identification using phase modulation and intensity modulation varies for different events; using both allows for coverage of various event identification scenarios. For example, for long-distance or high-insertion-loss optical fibers with low signal-to-noise ratios, weak events and weak-weak events can be identified through intensity modulation and demodulation. Similarly, strong-weak events and weak-strong events can be identified through phase modulation and demodulation. Therefore, the embodiments of this application provide more accurate event identification, greater applicability, and greater flexibility.

[0011] In one possible implementation, the encoded pulse generation module is used to output a phase encoded pulse to the modulation module during a first time period and an intensity encoded pulse to the modulation module during a second time period. The modulation module is used to perform phase modulation on the optical signal segment during the first time period according to the phase encoded pulse to obtain a phase pulse signal, and to perform intensity modulation on the optical signal segment during the second time period according to the intensity encoded pulse to obtain an intensity pulse signal. The optical pulse signal includes both the phase pulse signal and the intensity pulse signal.

[0012] In this implementation, the encoding pulse generation module generates different types of encoding pulses at different time periods: phase-encoded pulses for phase modulation and intensity-encoded pulses for intensity modulation. Based on this, the modulation module can accurately perform phase modulation and intensity modulation on optical signal segments at different time periods, ensuring the normal operation of both modulation processes.

[0013] In one possible implementation, the modulation module includes a phase modulation module and an intensity modulation module. The light source, the phase modulation module, and the intensity modulation module are sequentially connected to the optical fiber. The phase modulation module and the intensity modulation module are also connected to an coded pulse generation module, and the coded pulse includes a first DC signal and a second DC signal. The coded pulse generation module is used to output a phase coded pulse to the phase modulation module and the first DC signal to the intensity modulation module during a first time period, and to output a second DC signal to the phase modulation module and an intensity coded pulse to the intensity modulation module during a second time period. The phase modulation module is used to perform phase modulation on the optical signal segment during the first time period according to the phase coded pulse to obtain a phase pulse signal; the intensity modulation module is used to transmit the phase pulse signal according to the first DC signal. The phase modulation module is used to transmit the optical signal segment during the second time period according to the second DC signal; the intensity modulation module is used to perform intensity modulation on the optical signal segment during the second time period according to the intensity coded pulse to obtain an intensity pulse signal.

[0014] In one possible implementation, the modulation module includes a phase modulation module and an intensity modulation module. The light source, intensity modulation module, and phase modulation module are sequentially connected to the optical fiber. The phase modulation module and intensity modulation module are also connected to an encoded pulse generation module, and the encoded pulse includes a first DC signal and a second DC signal. The encoded pulse generation module outputs a phase encoded pulse to the phase modulation module and a first DC signal to the intensity modulation module during a first time period, and outputs a second DC signal to the phase modulation module and an intensity encoded pulse to the intensity modulation module during a second time period. The intensity modulation module transmits the optical signal segment within the first time period based on the first DC signal. The phase modulation module modulates the phase of the optical signal segment within the first time period based on the phase encoded pulse to obtain a phase pulse signal. The intensity modulation module modulates the intensity of the optical signal segment within the second time period based on the intensity encoded pulse to obtain an intensity pulse signal. The phase modulation module transmits the intensity pulse signal based on the second DC signal.

[0015] In both implementation methods described above, the phase modulation and intensity modulation processes are implemented using different modulation modules. During the first time period, the phase modulation module performs phase modulation to obtain a phase pulse signal, while the intensity modulation module remains in a pass-through state to avoid affecting the phase pulse signal. During the second time period, the intensity modulation module performs intensity modulation to obtain an intensity pulse signal, while the phase modulation module remains in a pass-through state to avoid affecting the intensity pulse signal. Therefore, the optical pulse signal output by the modulation module can include alternating phase and intensity pulse signals, making it possible to perform phase modulation and intensity modulation separately in different time periods.

[0016] In one possible implementation, the event signal includes a first event signal and a second event signal, wherein the first event signal is obtained by phase demodulation and the second event signal is obtained by intensity demodulation. Alternatively, the event signal is obtained by combining the first event signal and the second event signal.

[0017] In other words, this application can obtain two different event signals and identify the event through these two signals. This method eliminates the need to merge different event signals, making it simple, fast, and efficient. Alternatively, this application can also obtain a single event signal and identify the event through this signal. This event signal corresponds to a curve, which can more intuitively represent the event occurring in the optical fiber.

[0018] In one possible implementation, the processing module is used to acquire a first signal segment in the first event signal, wherein the power of the first signal segment is greater than or equal to a first power threshold; the processing module is used to acquire a second signal segment in the second event signal, wherein the power of the second signal segment is less than a second power threshold, and the second power threshold is less than or equal to the first power threshold; the processing module is used to merge the first signal segment and the second signal segment to obtain the event signal.

[0019] The first event signal is obtained through phase demodulation. Phase demodulation is ineffective at identifying weak events with low power. Therefore, selecting a first signal segment with higher power (i.e., greater than or equal to the first power threshold) from the first event signal avoids using the phase demodulation process to identify weak events, making it easier to identify strong events (including but not limited to strong-weak events and weak-strong events) through the first signal segment, resulting in higher identification accuracy. The second event signal is obtained through intensity demodulation. Intensity demodulation is ineffective at identifying strong-weak events or weak-strong events. Therefore, selecting a second signal segment with lower power (i.e., less than the second power threshold) from the second event signal avoids using the intensity demodulation process to identify strong-weak events or weak-strong events (these events include strong events and have high power, so selecting a second signal segment with lower power avoids this), resulting in higher identification accuracy.

[0020] In one possible implementation, the encoded pulse generation module includes a digital pulse generation module and a digital-to-analog conversion module, which are sequentially connected to the modulation module. The digital pulse generation module generates encoded pulses in digital form and outputs them to the digital-to-analog conversion module. The digital-to-analog conversion module converts the encoded pulses in digital form into encoded pulses in analog form and outputs them to the modulation module.

[0021] In this implementation, digital encoded pulses are generated, and analog encoded pulses are obtained through a digital-to-analog conversion process, so that the modulation module can complete modulation based on the analog encoded pulses.

[0022] In one possible implementation, the encoded pulse generation module includes a timing control module and an analog pulse generation module, which are sequentially connected to the modulation module. The timing control module generates a timing control signal and outputs the timing control signal to the analog pulse generation module. The analog pulse generation module generates an analog encoded pulse based on the timing control signal and outputs the analog encoded pulse to the modulation module.

[0023] In this implementation, there is no need to generate digital coded pulses; analog coded pulses can be generated directly based on the timing control signal. This is simple and fast, and enables the modulation module to complete modulation based on analog coded pulses.

[0024] In one possible implementation, the ratio of the first quantity to the second quantity is a first proportion, where the first quantity is the number of phase-coded pulses output in the first time period, and the second quantity is the number of intensity-coded pulses output in the second time period. Alternatively, the ratio of the duration of the first time period to the duration of the second time period is a second proportion.

[0025] This implementation method allows for flexible adjustment of the proportions of phase modulation and intensity modulation processes in the fiber optic detection process, making it easier to adapt to different event recognition scenarios. For example, since phase modulation is less effective at recognizing weak events, its proportion can be reduced when there are many weak events in the fiber, while its proportion can be increased when there are many strong events.

[0026] In a second aspect, an optical line terminal (OLT) is provided, the OLT including the fiber optic detection device provided in the first aspect or any possible implementation thereof.

[0027] Thirdly, a method for identifying events is provided. In this method, an electrical signal is obtained based on an optical signal and a return signal. The return signal is output by an optical fiber based on an optical pulse signal. The optical pulse signal is obtained by performing phase modulation and intensity modulation on optical signal segments within different time periods according to coded pulses. The electrical signal segments within different time periods are demodulated in phase and intensity to obtain an event signal. The event signal is used to identify events occurring in the optical fiber, and the electrical signal segments correspond to the optical signal segments.

[0028] In one possible implementation, the event signal includes a first event signal and a second event signal, wherein the first event signal is obtained by phase demodulation and the second event signal is obtained by intensity demodulation. Alternatively, the event signal is obtained by combining the first event signal and the second event signal.

[0029] In one possible implementation, phase demodulation and intensity demodulation are performed on electrical signal segments within different time periods to obtain an event signal, including: performing phase demodulation on electrical signal segments within different time periods to obtain a first event signal; acquiring a first signal segment from the first event signal, wherein the power of the first signal segment is greater than or equal to a first power threshold; performing intensity demodulation on electrical signal segments within different time periods to obtain a second event signal; acquiring a second signal segment from the second event signal, wherein the power of the second signal segment is less than a second power threshold, and the second power threshold is less than or equal to the first power threshold; and merging the first signal segment and the second signal segment to obtain the event signal.

[0030] Fourthly, a chip is provided, including a processor for retrieving and executing instructions stored in a memory, causing a communication device on which the chip is mounted to perform the method provided in the third aspect or any possible implementation thereof.

[0031] Fifthly, another chip is provided, including an input interface, an output interface, a processor, and a memory. The input interface, output interface, processor, and memory are interconnected via internal connection paths. The processor is used to execute code in the memory, and when the code is executed, the processor is used to perform the methods provided in the third aspect or any possible implementation thereof.

[0032] It should be understood that the technical effects achieved by the technical solutions and corresponding possible implementations of the second to fifth aspects of this application can be referred to the technical effects achieved by the technical solutions and corresponding possible implementations of the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0033] Figure 1 This application provides a schematic diagram of the structure of an optical access network according to an embodiment of the present application.

[0034] Figure 2 A schematic diagram of the structure of an optical time domain reflectometer (OTDR) system provided in an embodiment of this application;

[0035] Figure 3 A schematic diagram of a strong and weak event provided in an embodiment of this application;

[0036] Figure 4 This is a schematic diagram of the structure of an optical fiber detection device provided in an embodiment of this application;

[0037] Figure 5 This is a schematic diagram of the structure of an encoded pulse generation module provided in an embodiment of this application;

[0038] Figure 6 This is a schematic diagram of another coded pulse generation module provided in an embodiment of this application;

[0039] Figure 7 This is a schematic diagram of another optical fiber detection device provided in an embodiment of this application;

[0040] Figure 8 A schematic diagram of an coded pulse provided for an embodiment of this application;

[0041] Figure 9 A schematic diagram illustrating the transmission of an encoded pulse, provided as an embodiment of this application;

[0042] Figure 10 This is a schematic diagram of the structure of another optical fiber detection device provided in the embodiments of this application;

[0043] Figure 11 This is a schematic diagram of the structure of another optical fiber detection device provided in the embodiments of this application;

[0044] Figure 12 This is a schematic diagram of the structure of another optical fiber detection device provided in the embodiments of this application;

[0045] Figure 13 This is a schematic diagram of the structure of another optical fiber detection device provided in the embodiments of this application;

[0046] Figure 14 This is a schematic diagram of the structure of another optical fiber detection device provided in the embodiments of this application;

[0047] Figure 15 This is a schematic diagram of the structure of another optical fiber detection device provided in the embodiments of this application;

[0048] Figure 16 A flowchart for obtaining an OTDR curve is provided as an embodiment of this application;

[0049] Figure 17 A flowchart illustrating another method for obtaining an OTDR curve, as provided in this application embodiment;

[0050] Figure 18 This is a flowchart illustrating a method for identifying events provided in an embodiment of this application. Detailed Implementation

[0051] The terminology used in the implementation section of this application is for the purpose of explaining specific embodiments of this application only, and is not intended to limit this application.

[0052] With the continuous development of optical communication technology, optical fibers are widely used in optical access networks, buried pipelines, perimeter monitoring and early warning lines, submarine optical cables, and underground exploration lines. Optical fiber detection devices can identify events occurring in the optical fiber, facilitating maintenance and ensuring its normal operation in various scenarios.

[0053] Optical access networks are used to connect user terminals (such as mobile phones or computers) to the network. Passive optical networks (PONs) are a type of optical access network. Figure 1 As shown, a PON includes an OLT, an optical distribution network (ODN), and user-side equipment. The ODN includes optical fibers and passive optical splitters (POS), while the user-side equipment includes optical network terminals (ONTs) or optical network units (ONUs). The OLT is connected to the user-side equipment via the optical fibers and POS components within the ODN. Thus, user terminals can access the network and achieve internet access through the user-side equipment, optical fibers, splitters, and the OLT.

[0054] Fiber optic testing devices can detect the fiber optic links between the OLT and user-side equipment (also known as the fiber optic links between the OLT and user-side equipment) to identify events occurring in the fiber optic network. This facilitates maintenance based on these events, ensuring the normal operation of the PON. Taking an OTDR (Optical Time Detector) as an example, during fiber optic testing, the OTDR sends an optical signal into the fiber. As the signal propagates within the fiber, Rayleigh backscattering (RBS) and Fresnel reflection occur on the inner wall of the fiber and the devices connected to it, forming a return signal—the signal returned from the fiber to the OTDR. Devices connected to the fiber optic network include, but are not limited to, POS (Positioning Point of Sale) devices or devices connected to the fiber optic ends (such as ONTs or ONUs, etc., user-side equipment). The OTDR receives and demodulates the return signal to obtain an event signal. This event signal is used to identify events occurring in the fiber optic network, such as fiber bending, fiber breakage (i.e., fiber breakage location), events occurring in user-side equipment connected to the fiber (i.e., location and monitoring of user-side equipment events), and port detection (i.e., port visualization) of user-side equipment connected to the fiber, thereby improving the utilization of communication resources and maintenance efficiency.

[0055] In addition, fiber optic detection devices can prevent intrusion into buried pipelines, perimeter monitoring and early warning lines, or submarine optical cables. For example, an intrusion event will cause vibration, which will affect the optical fiber. The fiber optic detection device receives the returned signal, and by demodulating and identifying the returned signal, it can detect the intrusion event and achieve the intrusion prevention function. Fiber optic detection devices can also extract information from underground exploration lines. For example, by generating underground vibration waves through an active excitation source, these waves propagate through geology with different compositions and structures. The optical fiber will be affected by the propagated underground vibration waves. The fiber optic detection device receives the returned signal, and by demodulating and identifying the returned signal, it can obtain the composition and structure information at different depths underground, which can be used to guide the underground mining process. Of course, in addition to the composition and structure information exemplified here, fiber optic detection devices can also extract other information to provide sensing functions. Other information includes, but is not limited to, sound waves, vibration, temperature, or stress, etc., which are not limited in this application embodiment.

[0056] Optionally, events can be categorized into reflective events and non-reflective events. Reflective events are those caused by Fresnel reflection, including but not limited to reflections at joints, fiber breaks, and ONTs or ONUs. Non-reflective events are those caused by RBSs, including but not limited to non-reflective events caused by fiber fusion splice loss, bending loss, etc.

[0057] Alternatively, events can be categorized based on the power of the returned and event signals. However, due to power loss in optical fibers (up to 30 dB or more) and varying reflection power from different components within the fiber optic cable or its connections, the power of the returned and event signals may differ. Events with higher power are considered strong events, while those with lower power are considered weak events. Event identification scenarios include: identifying a single strong event, identifying a single weak event, identifying strong-weak events, identifying weak-strong events, identifying strong-strong events, or identifying weak-weak events. Strong-weak events are those where adjacent events consist of a strong event followed by a weak event; weak-strong events are those where adjacent events consist of a weak event followed by a strong event; strong-strong events are those where all adjacent events are strong; and weak-weak events are those where all adjacent events are weak.

[0058] To achieve event identification, fiber optic detection devices can employ a single-pulse detection scheme, where the optical signal sent into the fiber is a single pulse. However, this detection scheme presents a trade-off between spatial resolution and sensing distance. A smaller pulse width results in higher spatial resolution but reduces the sensing distance. In situations requiring higher spatial resolution (e.g., identifying ONTs at different ports, i.e., when multiple ONTs are connected at the fiber optic end), a higher spatial resolution (e.g., ≤0.2 meters) is required, necessitating the use of a smaller pulse width. However, using a smaller pulse width leads to a reduction in sensing distance.

[0059] To address this, optical pulse coding technology can be employed. Appropriate coded pulse signals are obtained through coding (also known as modulation), and these signals are used as detection signals. In other words, the optical signal sent by the fiber optic detection device into the fiber is the coded pulse signal. This method neither reduces spatial resolution nor compromises sensing distance, thus effectively resolving the contradiction between spatial resolution and sensing distance.

[0060] like Figure 2 As shown, optical pulse coding technology is implemented through either a coherent OTDR system (solid and dashed lines) or a direct-detection OTDR system (solid line). In the coherent OTDR system, a phase modulator (or an intensity modulator in the direct-detection OTDR system) encodes a coded pulse signal based on the optical signal transmitted from the light source and the coded codewords transmitted by the waveform generator. This coded pulse signal is then transmitted into an optical fiber. A photodetector receives the returned signal from the optical fiber and performs photoelectric conversion. A digital processor decodes (also known as demodulation) the photoelectric converted signal to obtain an event signal used for event identification. The width of the coded codeword (code width) corresponds to the spatial resolution, and the length of the coded codeword (code length) corresponds to the sensing distance. Decreasing the code width improves spatial resolution, while increasing the code length increases the sensing distance.

[0061] In related technology one, the phase modulator in a coherent OTDR system employs a single phase coding scheme. The coded pulse signal is obtained through phase modulation, and phase demodulation is required when demodulating the returned signal. However, phase demodulation is susceptible to noise. When the power of the returned signal is low, the impact of noise is more severe in long-distance or high-insertion-loss scenarios, leading to lower accuracy in identifying weak and weak-weak events. Therefore, phase modulation (and corresponding phase demodulation) is suitable for identifying individual strong events, strong-weak events, weak-strong events, and strong-strong events.

[0062] In related technology two, the intensity modulator in the direct-detection OTDR system uses a single intensity coding scheme. The coded pulse signal is obtained through intensity modulation, and intensity demodulation is required when demodulating the return signal. Compared to phase demodulation, intensity demodulation tends to result in lower sidelobe suppression of the event signal. The sidelobe suppression ratio (PSR) is the ratio of the peaks of the main lobe to those of nearby side lobes; a lower PSR indicates a less distinct distinction between the main lobe and side lobes. This can easily lead to confusion between adjacent events, and the confusion is more severe when adjacent events include both strong and weak events. The reason for this is that, for example... Figure 3 As shown, when adjacent events include strong and weak events, the strong event corresponds to the main lobe, and the weak event corresponds to the side lobe. Due to the low suppression ratio of the side lobe, the hook corresponding to the weak event is large, making it difficult to distinguish between strong and weak events, thus causing confusion. This results in low accuracy in identifying strong-weak events or weak-strong events. Therefore, intensity modulation (and the corresponding intensity demodulation) is suitable for identifying individual strong events, individual weak events, strong-strong events, and weak-weak events.

[0063] Therefore, phase modulation and intensity modulation are suitable for identifying different events. Generally speaking, phase modulation is more suitable for situations where strong events need to be identified, while intensity modulation is more suitable for identifying events other than strong-weak and weak-strong events. Both related technologies one and two suffer from relatively low accuracy in event identification, exhibiting certain limitations.

[0064] This application provides an optical fiber detection device, such as an OTDR. Figure 4 As shown, the fiber optic detection device includes a light source 1, an encoded pulse generation module 2, a modulation module 3, a photoelectric detection module 4, and a processing module 5. The light source 1 and the encoded pulse generation module 2 are respectively connected to the modulation module 3, and the light source 1 and the processing module 5 are respectively connected to the photoelectric detection module 4. The modulation module 3 and the photoelectric detection module 4 are also respectively connected to optical fibers. Next, [the following will be discussed]... Figure 4 The functions of each module shown are explained below.

[0065] Light source 1 is used to output optical signals to modulation module 3 and photoelectric detection module 4 respectively. The optical signal output by light source 1 is a continuous optical signal, which includes multiple optical signal segments.

[0066] Encoded pulse generation module 2 is used to output encoded pulses to modulation module 3. Encoded pulses can also be called encoded codewords or encoded pulse sequences.

[0067] Modulation module 3 is used to perform phase modulation and intensity modulation on optical signal segments within different time periods of the optical signal according to the encoded pulses, thereby obtaining optical pulse signals and outputting them to the optical fiber, causing the optical fiber to output a return signal. Since light source 1 outputs optical signals to modulation module 3 and encoded pulse generation module 2 outputs encoded pulses to modulation module 3, modulation module 3 can receive both the optical signal and the encoded pulses. Therefore, it can perform phase modulation and intensity modulation on optical signal segments within different time periods of the optical signal according to the encoded pulses, thereby obtaining optical pulse signals. Phase modulation can also be called phase encoding, intensity modulation can also be called intensity encoding, and the optical pulse signal can also be called an encoded pulse signal. Modulation module 3 outputs optical pulse signals to the optical fiber. During the propagation of the optical pulse signal within the optical fiber, the inner wall of the optical fiber and the devices connecting the optical fiber perform at least one of RBS or Fresnel reflection on the optical pulse signal, thereby forming a return signal. The return signal is in optical form, and its propagation direction is opposite to that of the optical pulse signal. Therefore, the optical fiber can output this return signal to the optical fiber detection device.

[0068] In this embodiment of the application, performing phase modulation and intensity modulation on optical signal segments in different time periods (i.e., there are multiple optical signal segments) means that for each optical signal segment in each time period, phase modulation or intensity modulation is performed, so that among the multiple optical signal segments, some optical signal segments are phase modulated and other optical signal segments are intensity modulated.

[0069] The photoelectric detection module 4 is used to acquire an electrical signal based on the optical signal and the return signal, and output the electrical signal to the processing module 5. Since the light source 1 outputs an optical signal to the photoelectric detection module 4, the photoelectric detection module 4 can receive the optical signal. As explained above, the optical fiber can output a return signal to the optical fiber detection device, and therefore the photoelectric detection module 4 can receive the return signal. The photoelectric detection module 4 has a photoelectric conversion function, capable of converting optical signals into electrical signals. Since the return signal is an optical signal, the photoelectric detection module 4 can acquire an electrical signal based on the optical signal and the return signal; the electrical signal is thus an electrical signal.

[0070] Since the aforementioned optical signal includes optical signal segments across multiple time periods, the electrical signal also correspondingly includes electrical signal segments across multiple time periods (i.e., multiple electrical signal segments exist). Each optical signal segment corresponds one-to-one with a specific electrical signal segment. The electrical signal segment corresponding to an optical signal segment refers to the segment obtained after the optical signal segment has undergone modulation by modulation module 3, propagation through the optical fiber, and photoelectric conversion by photoelectric detection module 4. For each optical signal segment, if the optical signal segment is phase-modulated, the corresponding electrical signal segment needs to be phase-demodulated; if the optical signal segment is intensity-modulated, the corresponding electrical signal segment needs to be intensity-demodulated.

[0071] Processing module 5 performs phase demodulation and intensity demodulation on electrical signal segments at different time periods to obtain event signals. These event signals are used to identify events occurring in the optical fiber. The electrical signal segments correspond to the optical signal segments. Since photodetector module 4 outputs electrical signals to processing module 5, processing module 5 receives these electrical signals. For each electrical signal segment, if the corresponding optical signal segment is phase-modulated, phase demodulation is performed on that segment; if the corresponding optical signal segment is intensity-modulated, intensity demodulation is performed. Phase demodulation can also be called phase decoding, and intensity demodulation can also be called intensity decoding.

[0072] Based on the functions of each module described above, it can be seen that in this embodiment of the application, the optical fiber detection device performs both phase modulation and corresponding phase demodulation, as well as intensity modulation and corresponding intensity demodulation. For different events, the accuracy of identification using phase modulation and intensity modulation is different. Using both phase modulation and intensity modulation can cover a variety of event identification scenarios, making the event identification more accurate, more applicable, and more flexible.

[0073] In an exemplary embodiment, the above-described modules can be implemented in hardware, as detailed in the following examples.

[0074] Optionally, the light source 1 is, for example, a laser, including but not limited to a tunable laser or a narrow linewidth laser.

[0075] In an exemplary embodiment, the encoded pulse generation module 2 includes, but is not limited to, the following two types.

[0076] The first type of encoded pulse generation module 2. For example... Figure 5 As shown, the encoded pulse generation module 2 includes a digital pulse generation module 21 and a digital-to-analog conversion module 22, which are sequentially connected to the modulation module 3.

[0077] The digital pulse generation module 21 generates digital coded pulses and outputs them to the digital-to-analog converter module 22. The digital-to-analog converter module 22 converts the digital coded pulses into analog coded pulses and outputs them to the modulation module 3. In one example, the analog coded pulse is an analog voltage signal.

[0078] For example, the encoded pulse includes a phase-coded pulse for phase modulation and an intensity-coded pulse for intensity modulation. The digital pulse generation module 21 can generate digital phase-coded pulses and digital intensity-coded pulses respectively, according to the configuration. Correspondingly, the digital-to-analog converter module 22 converts the digital phase-coded pulses into analog phase-coded pulses and the digital intensity-coded pulses into analog intensity-coded pulses, outputting the analog phase-coded pulses and analog intensity-coded pulses to the modulation module 3 respectively. The functions of the digital pulse generation module 21 and the digital-to-analog converter module 22 will be further explained below in conjunction with the structure of the modulation module 3; detailed descriptions are omitted here.

[0079] Optionally, the digital pulse generation module 21 is a digital circuit capable of generating signals in digital form (i.e., digital signals). Digital signals are discrete-time signals. Examples of digital circuits include field-programmable gate arrays (FPGAs). The digital-to-analog conversion module 22 includes, but is not limited to, digital-to-analog conversion circuits, which are also called digital-to-analog converters (DACs).

[0080] The second type of encoded pulse generation module 2. For example... Figure 6 As shown, the encoded pulse generation module 2 includes a timing control module 23 and an analog pulse generation module 24, which are sequentially connected to the modulation module 3.

[0081] The timing control module 23 generates timing control signals and outputs them to the analog pulse generation module 24. The analog pulse generation module 24 generates analog coded pulses based on the timing control signals and outputs them to the modulation module 3.

[0082] For example, the encoded pulse includes a phase-coded pulse for phase modulation and an intensity-coded pulse for intensity modulation. The timing control module 23 can generate timing control signal A and timing control signal B according to the configuration. Correspondingly, the analog pulse generation module 24 is used to generate an analog phase-coded pulse based on timing control signal A, and an analog intensity-coded pulse based on timing control signal B, and outputs the analog phase-coded pulse and analog intensity-coded pulse to the modulation module 3 respectively. The functions of the timing control module 23 and the analog pulse generation module 24 will be further explained below in conjunction with the structure of the modulation module 3; detailed explanations are omitted here.

[0083] Optionally, the timing control module 23 includes, but is not limited to, control circuitry. The analog pulse generation module 24 is an analog circuit capable of generating analog signals (i.e., analog signals), which are continuous signals in time.

[0084] In an exemplary embodiment, the modulation module 3 includes, but is not limited to, the following two types.

[0085] The first type of modulation module 3 includes multiple modulators. Some modulators are used for phase modulation of the optical signal segment (which can be referred to as phase modulation module 31), and others are used for intensity modulation of the optical signal segment (which can be referred to as intensity modulation module 32). For example, modulation module 3 includes two modulators: one for phase modulation of the optical signal segment and the other for intensity modulation. Alternatively, it may include three modulators: two (modulator A and modulator B) for phase modulation of the optical signal segment and one (modulator C) for intensity modulation. Modulator A is the primary modulator, and modulator B is the backup modulator. When modulator A is functioning normally, it performs phase modulation of the optical signal segment; when modulator A malfunctions, modulator B performs phase modulation. Modulator C performs intensity modulation of the optical signal segment.

[0086] Optionally, the modulator used for phase modulation includes in-phase quadrature modulators, etc., and the modulator used for intensity modulation includes at least one of the following: in-phase quadrature modulator, electro-optic modulator, acousto-optic modulator, or semiconductor optical amplifier, etc.

[0087] The second type of modulation module 3 is a separate modulator that is used for both phase modulation and intensity modulation of the optical signal segment. Optionally, this modulator includes in-phase quadrature modulators, etc.

[0088] For example, the photoelectric detection module 4 includes a filtering unit and a calculation unit. The filtering unit is used to filter the optical signal to obtain the filtered signal, and the calculation unit is used to sample the filtered signal to obtain sampling points, and to perform calculations on the sampling points in adjacent or certain ranges (the calculation method is not limited) to obtain the electrical signal.

[0089] Optionally, the filtering unit includes a filtering circuit, and the computing unit includes a microcontroller unit (MCU) or a digital signal processing (DSP) chip, etc.

[0090] For example, the processing module 5 includes, but is not limited to, an MCU or a DSP chip.

[0091] In addition to the modules described above, the fiber optic testing device may also include other modules, combined with... Figure 7 Let's illustrate with examples.

[0092] The first type of other module, the first coupler 71 and the second coupler 72, such as Figure 7 As shown, the light source 1, the modulation module 3, and the second coupler 72 are respectively connected to the first coupler 71, and the second coupler 72 is also connected to the optical fiber and the photoelectric detection module 4.

[0093] The first coupler 71 is used to split the optical signal output from the light source 1 into signal light and local oscillator light (also called reference light). The signal light and local oscillator light are coherent light, which refers to light with the same frequency, the same vibration direction, and a constant phase difference. The first coupler 71 is also used to output signal light to the modulation module 3, so that the modulation module 3 can perform phase modulation and intensity modulation on the optical signal segments in different time periods of the signal light according to the encoded pulse to obtain an optical pulse signal, and output the optical pulse signal to the optical fiber, so that the optical fiber outputs a return signal. This will not be elaborated here. The first coupler 71 is also used to output local oscillator light to the second coupler 72.

[0094] The second coupler 72 is used to perform beat frequency processing on the return signal and the local oscillator light output from the optical fiber to obtain a beat frequency signal. Since both the return signal and the local oscillator light are optical signals, the beat frequency signal is also an optical signal. The second coupler 72 is also used to output the beat frequency signal to the photodetector module 4, so that the photodetector module 4 can perform photoelectric conversion on the beat frequency signal to obtain and output an electrical signal to the processing module 5. That is, the photodetector module 4 obtains an electrical signal based on the optical signal and the return signal, which may include: the photodetector module 4 performs photoelectric conversion on the beat frequency signal to obtain an electrical signal, which is obtained based on the optical signal (e.g., the local oscillator light in the optical signal) and the return signal.

[0095] Optionally, the function of the first coupler 71 can be integrated inside the light source 1, and the function of the second coupler 72 can be integrated inside the photoelectric detection module 4. For example, combined with... Figure 4 An optical signal is generated in light source 1, which is then divided into signal light and local oscillator light. Light source 1 outputs optical signals to modulation module 3 and photodetector module 4, respectively, including: light source 1 outputs signal light to modulation module 3 and local oscillator light to photodetector module 4. Photodetector module 4 obtains an electrical signal based on the optical signal and the return signal, including: photodetector module 4 performs beat frequency processing on the return signal and local oscillator light output from the optical fiber to obtain a beat frequency signal, and performs photoelectric conversion on the beat frequency signal to obtain an electrical signal. Then, photodetector module 4 can output an electrical signal to processing module 5.

[0096] The second type of module, circulator 73, includes modulation module 3, photodetector module 4 (or second coupler 72), and optical fiber, all connected to circulator 73. Based on this, the modulation module 3 outputs an optical pulse signal to the optical fiber via circulator 73. The optical fiber outputs a return signal via circulator 73 to photodetector module 4 (or second coupler 72).

[0097] Optionally, the circulator 73 includes a first port, a second port, and a third port. Figure 7 (Not shown in the diagram), modulation module 3 is connected to circulator 73 through the first port, photodetector module 4 (or second coupler 72) is connected to circulator 73 through the second port, and optical fiber is connected to circulator 73 through the third port. After modulation module 3 outputs an optical pulse signal, the optical pulse signal enters circulator 73 through the first port and exits circulator 73 through the third port, thus realizing the output of optical pulse signal to optical fiber. After optical fiber outputs a return signal, the return signal enters circulator 73 through the third port and exits circulator 73 through the second port, thus realizing the output of return signal to photodetector module 4 (or second coupler 72).

[0098] A third alternative module includes at least one of a first amplifier 74 and a second amplifier 75, where the first amplifier 74 amplifies the optical pulse signal and the second amplifier 75 amplifies the return signal. In the case where the fiber optic detection device includes a circulator 73, the first amplifier 74 is located between the modulation module 3 and the circulator 73, and the second amplifier 75 is located between the photodetector module 4 (or the second coupler 72) and the circulator 73. Alternatively, in the case where the fiber optic detection device does not include a circulator 73, the first amplifier 74 is located between the modulation module 3 and the optical fiber, and the second amplifier 75 is located between the photodetector module 4 (or the second coupler 72) and the optical fiber.

[0099] The structure of the fiber optic testing device was illustrated above. The functions of some of the modules included in the fiber optic testing device will now be explained in detail.

[0100] As mentioned above, the encoding pulse includes a phase encoding pulse and an intensity encoding pulse. For example, the encoding method corresponding to the phase encoding pulse includes, but is not limited to, Golay phase encoding, and the encoding method corresponding to the intensity encoding pulse can be simplex encoding, pseudo-random encoding, or Golay intensity encoding, etc. The embodiments of this application do not limit the encoding method.

[0101] The encoding pulse generation module 2 is used to output phase encoded pulses to the modulation module 3 during a first time period and to output intensity encoded pulses to the modulation module 3 during a second time period. The modulation module 3 is used to perform phase modulation on the optical signal segment during the first time period according to the phase encoded pulses to obtain a phase pulse signal, and to perform intensity modulation on the optical signal segment during the second time period according to the intensity encoded pulses to obtain an intensity pulse signal. The optical pulse signal includes both the phase pulse signal and the intensity pulse signal.

[0102] In one example, the number of phase-coded pulses output by the coded pulse generation module 2 during the first time period is denoted as the first quantity, and the number of intensity-coded pulses output by the coded pulse generation module 2 during the second time period is denoted as the second quantity. The ratio of the first quantity to the second quantity is the first proportion. This embodiment does not limit the value of the first proportion; the value of the first proportion can be set based on experience or actual needs.

[0103] For example, the first quantity is 2, the second quantity is 4, and the first ratio is 2:4. Taking Golay phase coding and Golay intensity coding as examples, the two phase coding pulses can be seen in... Figure 8 In (a), C and D are all bipolar Golay codes. The codewords of bipolar Golay codes include 1 and -1. 1 can be represented by phase π in the phase-coded pulse, and -1 can be represented by phase 0 in the phase-coded pulse. The four intensity-coded pulses can be found in [reference needed]. Figure 8 In (b), Cp, Cn, Dp, and Dn are all unipolar Golay codes. The codewords of unipolar Golay codes include 1 and 0. 1 can be represented by a high level in the intensity coding pulse, and 0 can be represented by a low level in the intensity coding pulse.

[0104] Based on this, the encoded pulse generation module 2 can transmit encoded pulses in an adjacent manner, such that the first number of phase encoded pulses are adjacent to the second number of intensity encoded pulses. For example, see... Figure 9In step (a), a first number of phase-coded pulses are sent first, followed by a second number of intensity-coded pulses. Alternatively, a second number of intensity-coded pulses may be sent first, followed by a first number of phase-coded pulses. The first number of phase-coded pulses and the second number of intensity-coded pulses are considered a single group of coded pulses. The coded pulse generation module 2 can send multiple groups of coded pulses. Correspondingly, the modulation module 3 modulates multiple groups of optical pulse signals, and the optical fiber outputs multiple sets of return signals. The photoelectric detection module 4 can acquire multiple sets of electrical signals. For each group of electrical signals (or at least two groups of electrical signals), the processing module 5 performs phase demodulation and intensity demodulation on different segments of that group of electrical signals, and synthesizes the event signal, which helps improve the success rate and accuracy of event recognition. Optionally, the sending order of the phase-coded pulses and intensity-coded pulses can be the same or different for different groups of coded pulses; this embodiment does not limit this. For example, for each group of coded pulses, the phase-coded pulses are sent first, followed by the intensity-coded pulses. For example, for one set of coded pulses, the phase coded pulse is sent first and then the intensity coded pulse is sent; for another set of coded pulses, the intensity coded pulse is sent first and then the phase coded pulse is sent.

[0105] In another example, the ratio of the duration of the first time period to the duration of the second time period is a second ratio. Optionally, embodiments of this application can acquire an event recognition scenario, for example, by determining the event recognition scenario based on experience or by predicting the event recognition scenario. If the event recognition scenario indicates that the number of strong events is greater than a first threshold, then the duration of the first time period can be larger, that is, the duration of the first time period is positively correlated with the number of strong events, because the phase modulation and demodulation process is more suitable for identifying strong events, or in other words, the accuracy of identifying strong events is higher. If the event recognition scenario indicates that the number of weak events is greater than a second threshold, then the duration of the second time period can be larger, that is, the duration of the second time period is positively correlated with the number of weak events, because the intensity modulation and demodulation process is more suitable for identifying weak events, or in other words, the accuracy of identifying weak events is higher. Embodiments of this application do not limit the duration of the first time period and the duration of the second time period; they can be set according to experience or actual needs. The duration of the first time period and the duration of the second time period can be the same or different. For example, the duration of the first time period is 30 seconds, and the duration of the second time period is also 30 seconds.

[0106] Based on this, the encoded pulse generation module 2 can transmit encoded pulses in a time-division multiplexing manner. For example, see... Figure 9In example (b), the phase-coded pulse is sent first in the first time period, and then the intensity-coded pulse is sent in the second time period. Alternatively, the intensity-coded pulse is sent first in the second time period, and then the phase-coded pulse is sent in the first time period. This application does not limit the sending order of the phase-coded pulse and the intensity-coded pulse. The coded pulse generation module 2 can also send multiple sets of coded pulses to improve the success rate and accuracy of event recognition.

[0107] Based on the two types of encoded pulse generation modules 2 and two types of modulation modules 3 described above, there are four possible combinations of encoded pulse generation module 2 and modulation module 3. Examples of these four combinations are provided below, in conjunction with the functional descriptions of encoded pulse generation module 2 and modulation module 3 above.

[0108] In the first combination method, a first encoded pulse generation module 2 is combined with a first modulation module 3. The encoded pulse generation module 2 includes a digital pulse generation module 21 and a digital-to-analog converter (DAC) module 22. The DAC module 22 includes a first DAC module 221 and a second DAC module 222, which are respectively connected to the digital pulse generation module 21. The modulation module 3 includes a phase modulation module 31 and an intensity modulation module 32. The phase modulation module 31 is used to perform phase modulation on the optical signal segment, and the intensity modulation module 32 is used to perform intensity modulation on the optical signal segment.

[0109] In one example, see Figure 10 The light source 1, phase modulation module 31, and intensity modulation module 32 are sequentially connected to the optical fiber. Phase modulation module 31 and intensity modulation module 32 are also connected to the encoded pulse generation module 2. In addition to the phase encoded pulse and intensity encoded pulse described above, the encoded pulse also includes a first DC signal and a second DC signal. Specifically, the phase modulation module 31 and intensity modulation module 32 are connected to the encoded pulse generation module 2, with phase modulation module 31 connected to the first digital-to-analog converter module 221 and intensity modulation module 32 connected to the second digital-to-analog converter module 222.

[0110] During phase modulation (i.e., within the first time period), the encoded pulse generation module 2 is used to output a phase encoded pulse to the phase modulation module 31 and a first DC signal to the intensity modulation module 32 within the first time period. The phase modulation module 31 is used to perform phase modulation on the optical signal segment within the first time period according to the phase encoded pulse to obtain a phase pulse signal. The intensity modulation module 32 is used to transmit the phase pulse signal according to the first DC signal.

[0111] For example, during the first time period, the digital pulse generation module 21 generates a digital phase-coded pulse and a digital first DC signal, outputs the digital phase-coded pulse to the first digital-to-analog converter module 221, and outputs the digital first DC signal to the second digital-to-analog converter module 222. The first digital-to-analog converter module 221 converts the digital phase-coded pulse into an analog phase-coded pulse and outputs the analog phase-coded pulse to the phase modulation module 31. The phase modulation module 31 can perform phase modulation on the optical signal segment during the first time period according to the analog phase-coded pulse to obtain a phase pulse signal. The second digital-to-analog converter module 222 converts the digital first DC signal into an analog first DC signal and outputs the analog first DC signal to the intensity modulation module 32, so that the intensity modulation module 32 is in a pass-through state. Then, the intensity modulation module 32 can transmit the phase pulse signal to output the phase pulse signal to the optical fiber (including but not limited to outputting to the optical fiber through the first amplifier 74 and the circulator 73, which will not be repeated below).

[0112] During intensity modulation (i.e., within the second time period), the encoding pulse generation module 2 outputs a second DC signal to the phase modulation module 31 and an intensity encoding pulse to the intensity modulation module 32 within the second time period. The phase modulation module 31 transmits the optical signal segment within the second time period according to the second DC signal. The intensity modulation module 32 modulates the intensity of the optical signal segment within the second time period according to the intensity encoding pulse to obtain an intensity pulse signal.

[0113] For example, during the second time period, the digital pulse generation module 21 generates digital intensity-coded pulses and a digital second DC signal, outputs the digital second DC signal to the first digital-to-analog converter module 221, and outputs the digital intensity-coded pulses to the second digital-to-analog converter module 222. The first digital-to-analog converter module 221 converts the digital second DC signal into an analog second DC signal and outputs the analog second DC signal to the phase modulation module 31, enabling the phase modulation module 31 to be in a pass-through state. Thus, the phase modulation module 31 can transmit the optical signal segment during the second time period and output the optical signal segment during the second time period to the intensity modulation module 32. The second digital-to-analog converter module 222 converts the digital intensity-coded pulses into analog intensity-coded pulses and outputs the analog intensity-coded pulses to the intensity modulation module 32. The intensity modulation module 32 can perform intensity modulation on the optical signal segment during the second time period according to the analog intensity-coded pulses to obtain an intensity pulse signal, which is then output to the optical fiber.

[0114] See another example. Figure 11 Light source 1, intensity modulation module 32, and phase modulation module 31 are sequentially connected to the optical fiber (different from...). Figure 10(Corresponding example), the phase modulation module 31 and the intensity modulation module 32 are also connected to the coded pulse generation module 2 (and...). Figure 10 (The corresponding examples are the same, so I will not repeat them here.) The encoded pulse also includes a first DC signal and a second DC signal.

[0115] During phase modulation (i.e., within the first time period), the encoded pulse generation module 2 is used to output a phase encoded pulse to the phase modulation module 31 and a first DC signal to the intensity modulation module 32 within the first time period. The intensity modulation module 32 is used to transmit the optical signal segment within the first time period according to the first DC signal. The phase modulation module 31 is used to perform phase modulation on the optical signal segment within the first time period according to the phase encoded pulse to obtain a phase pulse signal.

[0116] For example, during the first time period, the digital pulse generation module 21 generates a digital phase-coded pulse and a digital first DC signal, outputs the digital phase-coded pulse to the first digital-to-analog converter module 221, and outputs the digital first DC signal to the second digital-to-analog converter module 222. The second digital-to-analog converter module 222 converts the digital first DC signal into an analog first DC signal and outputs the analog first DC signal to the intensity modulation module 32, so that the intensity modulation module 32 is in a pass-through state. Therefore, the intensity modulation module 32 can transmit the optical signal segment within the first time period to output the optical signal segment within the first time period to the phase modulation module 31. The first digital-to-analog converter module 221 converts the digital phase-coded pulse into an analog phase-coded pulse and outputs the analog phase-coded pulse to the phase modulation module 31. The phase modulation module 31 can perform phase modulation on the optical signal segment within the first time period according to the analog phase-coded pulse to output a phase pulse signal to the optical fiber.

[0117] During intensity modulation (i.e., within the second time period), the encoded pulse generation module 2 outputs a second DC signal to the phase modulation module 31 and an intensity encoded pulse to the intensity modulation module 32 within the second time period. The intensity modulation module 32 modulates the optical signal segment within the second time period according to the intensity encoded pulse to obtain an intensity pulse signal. The phase modulation module 31 transmits the intensity pulse signal according to the second DC signal.

[0118] For example, during the second time period, the digital pulse generation module 21 generates a digital intensity-coded pulse and a digital second DC signal, outputs the digital second DC signal to the first digital-to-analog converter module 221, and outputs the digital intensity-coded pulse to the second digital-to-analog converter module 222. The second digital-to-analog converter module 222 converts the digital intensity-coded pulse into an analog intensity-coded pulse and outputs the analog intensity-coded pulse to the intensity modulation module 32. The intensity modulation module 32 can modulate the optical signal segment during the second time period according to the analog intensity-coded pulse to obtain an intensity pulse signal. The first digital-to-analog converter module 221 converts the digital second DC signal into an analog second DC signal and outputs the analog second DC signal to the phase modulation module 31, so that the phase modulation module 31 is in a pass-through state, and the phase modulation module 31 can transmit the intensity pulse signal to output the intensity pulse signal to the optical fiber.

[0119] The second combination involves combining the first type of encoded pulse generation module 2 with the second type of modulation module 3. (See also...) Figure 12 The encoded pulse generation module 2 includes a digital pulse generation module 21 and a digital-to-analog converter module 22. The modulation module 3 is connected to the digital-to-analog converter module 22. The modulation module 3 is used for both phase modulation and intensity modulation of the optical signal segment. Compared to the first combination method, the second combination method here does not require the generation of a DC signal, thus saving power consumption.

[0120] During phase modulation (i.e., within the first time period), the coded pulse generation module 2 outputs a phase-coded pulse to the modulation module 3 within the first time period. The modulation module 3 modulates the optical signal segment within the first time period according to the phase-coded pulse to obtain a phase pulse signal, and outputs the phase pulse signal to the optical fiber. For example, within the first time period, the digital pulse generation module 21 generates a digital phase-coded pulse and outputs it to the digital-to-analog converter module 22. The digital-to-analog converter module 22 converts the digital phase-coded pulse into an analog phase-coded pulse and outputs it to the modulation module 3. The modulation module 3 can modulate the optical signal segment within the first time period according to the analog phase-coded pulse to obtain and output a phase pulse signal to the optical fiber.

[0121] During intensity modulation (i.e., within the second time period), the coded pulse generation module 2 outputs intensity coded pulses to the modulation module 3 within the second time period. The modulation module 3 modulates the optical signal segment within the second time period according to the intensity coded pulses to obtain an intensity pulse signal, which is then output to the optical fiber. For example, within the second time period, the digital pulse generation module 21 generates digital intensity coded pulses and outputs them to the digital-to-analog converter module 22. The digital-to-analog converter module 22 converts the digital intensity coded pulses into analog intensity coded pulses and outputs them to the modulation module 3. The modulation module 3 can modulate the optical signal segment within the second time period according to the analog intensity coded pulses, obtaining and outputting an intensity pulse signal to the optical fiber.

[0122] The third combination involves combining the second type of encoded pulse generation module 2 with the first type of modulation module 3. The encoded pulse generation module 2 includes a timing control module 23 and an analog pulse generation module 24. The analog pulse generation module 24 includes a first analog pulse generation module 241 and a second analog pulse generation module 242, which are respectively connected to the timing control module 23. The modulation module 3 includes a phase modulation module 31 and an intensity modulation module 32.

[0123] In one example, see Figure 13 The light source 1, phase modulation module 31, and intensity modulation module 32 are sequentially connected to the optical fiber. Phase modulation module 31 and intensity modulation module 32 are also connected to the encoded pulse generation module 2. In addition to the phase-coded pulse and intensity-coded pulse described above, the encoded pulse also includes a first DC signal and a second DC signal. Specifically, the phase modulation module 31 and intensity modulation module 32 are connected to the encoded pulse generation module 2, including: phase modulation module 31 is connected to the first analog pulse generation module 241, and intensity modulation module 32 is connected to the second analog pulse generation module 242.

[0124] During the phase modulation process (i.e., within the first time period), the timing control module 23 outputs a first control signal to the first analog pulse generation module 241 (i.e., ... Figure 6The corresponding timing control signal A in the description causes the first analog pulse generation module 241 to generate an analog phase-coded pulse and output it to the phase modulation module 31. The phase modulation module 31 can perform phase modulation on the optical signal segment within the first time period according to the analog phase-coded pulse to obtain a phase pulse signal. The timing control module 23 also outputs a second control signal to the second analog pulse generation module 242, causing the second analog pulse generation module 242 to generate an analog first DC signal and output it to the intensity modulation module 32. This puts the intensity modulation module 32 in a pass-through state, allowing it to transmit the phase pulse signal and output it to the optical fiber.

[0125] During intensity modulation (i.e., within the second time period), the timing control module 23 outputs a third control signal to the first analog pulse generation module 241, causing the first analog pulse generation module 241 to generate an analog second DC signal and output the analog second DC signal to the phase modulation module 31. This puts the phase modulation module 31 in a direct-through state, allowing it to transmit the optical signal segment within the second time period and output it to the intensity modulation module 32. The timing control module 23 also outputs a fourth control signal to the second analog pulse generation module 242 (i.e., ... Figure 6 The timing control signal B in the corresponding description causes the second analog pulse generation module 242 to generate an analog intensity-coded pulse and output the analog intensity-coded pulse to the intensity modulation module 32. The intensity modulation module 32 can perform intensity modulation on the optical signal segment in the second time period according to the analog intensity-coded pulse to obtain an intensity pulse signal and output the intensity pulse signal to the optical fiber.

[0126] See another example. Figure 14 Light source 1, intensity modulation module 32, and phase modulation module 31 are sequentially connected to the optical fiber (different from...). Figure 13 (Corresponding example), the phase modulation module 31 and the intensity modulation module 32 are also connected to the coded pulse generation module 2 (and...). Figure 13 (The corresponding examples are the same, so I will not repeat them here.) The encoded pulse also includes a first DC signal and a second DC signal.

[0127] During phase modulation (i.e., within the first time period), the timing control module 23 outputs a second control signal to the second analog pulse generation module 242, causing the second analog pulse generation module 242 to generate an analog first DC signal and output the analog first DC signal to the intensity modulation module 32. This puts the intensity modulation module 32 in a pass-through state, allowing it to transmit the optical signal segment within the first time period and output it to the phase modulation module 31. The timing control module 23 also outputs a first control signal to the first analog pulse generation module 241, causing it to generate an analog phase-coded pulse and output it to the phase modulation module 31. The phase modulation module 31 can then perform phase modulation on the optical signal segment within the first time period based on the analog phase-coded pulse to obtain a phase pulse signal, which is then output to the optical fiber.

[0128] During intensity modulation (i.e., within the second time period), the timing control module 23 outputs a fourth control signal to the second analog pulse generation module 242, causing the second analog pulse generation module 242 to generate an analog intensity-coded pulse and output it to the intensity modulation module 32. The intensity modulation module 32 can then modulate the optical signal segment within the second time period according to the analog intensity-coded pulse to obtain an intensity pulse signal. The timing control module 23 also outputs a third control signal to the first analog pulse generation module 241, causing the first analog pulse generation module 241 to generate an analog second DC signal and output it to the phase modulation module 31. This puts the phase modulation module 31 in a pass-through state, allowing it to transmit the intensity pulse signal and output it to the optical fiber.

[0129] The fourth combination involves combining the second type of encoded pulse generation module 2 with the second type of modulation module 3. (See also...) Figure 15 The encoded pulse generation module 2 includes a timing control module 23 and an analog pulse generation module 24. The modulation module 3 is connected to the analog pulse generation module 24. The modulation module 3 is used for both phase modulation and intensity modulation of the optical signal segment. Compared to the third combination method, the fourth combination method here does not require the generation of a DC signal, thus saving power consumption.

[0130] During the phase modulation process (i.e., within the first time period), the timing control module 23 outputs a first control signal to the analog pulse generation module 24 (i.e., ... Figure 6 The timing control signal A in the corresponding description causes the analog pulse generation module 24 to generate an analog phase-coded pulse. The modulation module 3 modulates the optical signal segment in the first time period according to the analog phase-coded pulse to obtain and output the phase pulse signal to the optical fiber.

[0131] During the intensity modulation process (i.e., during the second time period), the timing control module 23 outputs a fourth control signal to the analog pulse generation module 24 (i.e., Figure 6 The timing control signal B in the corresponding description causes the analog pulse generation module 24 to generate an analog intensity-coded pulse. The modulation module 3 modulates the optical signal segment in the second time period according to the analog intensity-coded pulse, and outputs the intensity pulse signal to the optical fiber.

[0132] The above, combined with Figures 10 to 15 Four different combinations are illustrated. Among them, Figures 10 to 15 The diagram shows the first coupler 71, the second coupler 72, the circulator 73, the first amplifier 74, and the second amplifier 75 (the functions of these modules can be found in [reference]). Figure 7 The corresponding explanations (which will not be repeated here) are provided to ensure the completeness of the accompanying drawings. However, Figures 10 to 15 These modules are not intended to limit the structure of the fiber optic testing device; they can be selectively configured according to actual needs. Of course, other modules (not shown) can also be selectively configured according to actual needs.

[0133] Regardless of the combination method used, modulation module 3 can output optical pulse signals to the optical fiber, causing the optical fiber to output a return signal. The photodetector module 4 then outputs an electrical signal to processing module 5 based on the return signal. As explained above, processing module 5 is used to perform phase demodulation and intensity demodulation on electrical signal segments within different time periods. Specifically, for each electrical signal segment, if the corresponding optical signal segment is phase-modulated, phase demodulation is performed on that segment; if the corresponding optical signal segment is intensity-modulated, intensity demodulation is performed.

[0134] Optionally, such as Figure 16 As shown, processing module 5 distinguishes different electrical signal segments based on different time periods in the electrical signal, so as to use an appropriate demodulation method (phase demodulation or intensity demodulation) to demodulate the electrical signal segments. The duration of the optical pulse signal is the same as the duration of the electrical signal. In the optical pulse signal, the phase-coded pulse is obtained by phase-coding the optical signal segment within the first time period; therefore, in the electrical signal, the electrical signal segment within the first time period is the segment that needs phase demodulation (i.e., phase decoding). In the optical pulse signal, the intensity-coded pulse is obtained by intensity-coding the optical signal segment within the second time period; therefore, in the electrical signal, the electrical signal segment within the second time period is the segment that needs intensity demodulation (i.e., intensity decoding).

[0135] For example, the duration of the optical pulse signal is 60 seconds. Seconds 1-10 include phase-coded pulses, seconds 11-30 include intensity-coded pulses, seconds 31-40 include phase-coded pulses, and seconds 41-60 include intensity-coded pulses. The first time segment includes seconds 1-10 and seconds 31-40, with a duration of 10 seconds. The second time segment has a duration of 20 seconds. Correspondingly, the duration of the return signal output from the optical fiber based on the optical pulse signal is also 60 seconds, and the duration of the electrical signal acquired by the photoelectric detection module 4 based on the return signal is also 60 seconds. Within the 60-second electrical signal, the electrical signal segment from seconds 1-10 requires phase demodulation, the electrical signal segment from seconds 11-30 requires intensity demodulation, the electrical signal segment from seconds 31-40 requires phase demodulation, and the electrical signal segment from seconds 41-60 requires intensity demodulation. Based on this, the processing module 5 can distinguish different electrical signal segments and thus adopt an appropriate demodulation method to demodulate the electrical signal segments.

[0136] As explained above, processing module 5 can obtain an event signal by performing phase demodulation and intensity demodulation. The event signal is used to identify events occurring in the optical fiber. In other words, the event signal is the signal to be measured. In an exemplary embodiment, the event signal can include the following two cases.

[0137] In the first scenario, the event signal includes a first event signal and a second event signal. The first event signal is obtained through phase demodulation, and the second event signal is obtained through intensity demodulation. That is, for electrical signal segments requiring phase demodulation, processing module 5 uses phase demodulation to restore the phase and intensity of the electrical signal segment, obtaining the first event signal. For electrical signal segments requiring intensity demodulation, processing module 5 uses intensity demodulation to restore the intensity of the electrical signal segment, obtaining the second event signal. In this embodiment, the first event signal and the second event signal reflect one or more identical events on the same optical fiber segment. However, due to the different demodulation methods used and the different information restored (phase and intensity, etc.), the power corresponding to the same event may differ in different event signals, thus affecting the accuracy of event identification.

[0138] Optionally, when restoring phase and intensity, the fiber optic detection device is, for example, a phase-sensitive OTDR, which can be used for distributed detection of information such as sound waves or vibrations. When restoring intensity, the fiber optic detection device is, for example, an OTDR. Of course, restoring phase and intensity (or restoring intensity) are just two examples; embodiments of this application can also restore other information according to actual needs. For example, processing module 5 can also restore the Brillouin scattering information of the electrical signal segment. In this case, the fiber optic detection device is, for example, a Brillouin scattering OTDR, which can be used for distributed detection of information such as temperature and stress. As another example, processing module 5 can also restore the polarization of the electrical signal segment. In this case, the fiber optic detection device is, for example, a polarization OTDR. Different types of OTDRs can be configured according to actual needs. Figures 4 to 7 , Figures 10 to 15 Devices not shown in the diagram.

[0139] Using location (in kilometers, referring to the distance from the fiber optic detection device) as the x-axis and power (in dB) as the y-axis, the first event signal can be represented as a first OTDR curve, and the second event signal can also be represented as a second OTDR curve. The first and second OTDR curves are two different OTDR curves, providing high spatial resolution. Optionally, in the first case, the processing module 5 can acquire the first and second OTDR curves separately. In one example, the processing module 5 outputs the first and second OTDR curves to display them to the user, who can then identify the event occurring in the fiber optic cable by browsing the curves. In another example, the processing module 5 identifies one or more first events based on the first OTDR curve and one or more second events based on the second OTDR curve. The processing module 5 outputs both the first and second events to display them to the user, who can then determine the event occurring in the fiber optic cable by browsing the curves.

[0140] In the second scenario, the event signal is obtained by merging the first event signal and the second event signal. For example, processing module 5 is used to acquire a first signal segment from the first event signal, where the power of the first signal segment is greater than or equal to a first power threshold. Since the first event signal is obtained through phase demodulation, and phase demodulation is less effective at identifying weak events with lower power, a first signal segment with higher power is selected from the first event signal. This avoids using phase demodulation to identify weak events, making it easier to identify strong events through the first signal segment. This aligns with the above description that phase modulation is more suitable for identifying events including strong events, resulting in higher accuracy. Processing module 5 is also used to acquire a second signal segment from the second event signal, where the power of the second signal segment is less than a second power threshold, which is less than or equal to the first power threshold. Since the second event signal is obtained through intensity demodulation, and intensity demodulation is less effective at identifying strong-weak or weak-strong events, a second signal segment with lower power is selected from the second event signal. This avoids using intensity demodulation to identify strong-weak or weak-strong events, making it easier to identify weak events through the second signal segment. This aligns with the above description that intensity modulation is more suitable for identifying events other than strong-weak and weak-strong events, resulting in higher accuracy. Processing module 5 is used to merge the first signal segment and the second signal segment to obtain the event signal.

[0141] In one example, processing module 5 can, as described above, use a certain data merging algorithm to merge the first signal segment and the second signal segment to obtain an event signal. The event signal is represented as an OTDR curve with position as the x-axis and power as the y-axis. This OTDR curve is the OTDR curve corresponding to the event signal and has high spatial resolution. Processing module 5 can output this OTDR curve or the event identified based on it, making it convenient for users to know about events occurring on the optical fiber.

[0142] See another example. Figure 16 The processing module 5 can acquire the first OTDR curve and the second OTDR curve as described in the first case above, and merge the first OTDR curve and the second OTDR curve using a certain data merging algorithm to achieve the merging of the first signal segment and the second signal segment, resulting in a single OTDR curve. This OTDR curve is the OTDR curve corresponding to the event signal and has high spatial resolution. The processing module 5 can output this OTDR curve or the event identified based on this OTDR curve, making it convenient for users to know about events occurring in the optical fiber.

[0143] For example, the first signal segment is the first curve segment in the first OTDR curve with power greater than or equal to the first power threshold, and the second signal segment is the second curve segment in the second OTDR curve with power less than the second power threshold. By smoothly splicing the first curve segment and the second curve segment, the first OTDR curve and the second OTDR curve can be merged to obtain a single OTDR curve.

[0144] Optionally, the first OTDR curve includes multiple first curve segments, each corresponding to one or more first events, which are events identified through a phase demodulation process. The second OTDR curve includes multiple second curve segments, each corresponding to one or more second events, which are events identified through an intensity demodulation process. For example, the processing module 5 can use the first OTDR curve as a reference. For each first curve segment, if the power of the first curve segment is greater than or equal to a first power threshold, the first curve segment is retained; if the power of the first curve segment is less than a second power threshold, the first curve segment is replaced with a second curve segment to obtain an OTDR curve. Alternatively, see [link to documentation]. Figure 17 The processing module 5 can also use the second OTDR curve as a reference. For each second curve segment, if the power of the second curve segment is less than the second power threshold, the second curve segment is retained; if the power of the second curve segment is greater than or equal to the first power threshold, the second curve segment is replaced with the first curve segment to obtain an OTDR curve. When the second power threshold and the first power threshold are the same, "less than the second power threshold" and "greater than or equal to the first power threshold" are two different intervals. When the second power threshold is less than the first power threshold, there is also a third interval, i.e., the power of the second curve segment is greater than or equal to the second power threshold and less than the first power threshold. For example, the processing module 5 can retain the second curve segment in this third interval.

[0145] The first OTDR curve described above includes multiple first sub-segments, each being the smallest unit of granularity in the first OTDR curve. The distance corresponding to each first sub-segment on the horizontal axis is a first distance (e.g., 0.2 meters). Each first event includes multiple first sub-segments; therefore, since each first curve segment corresponds to one or more first events, each first curve segment also includes multiple first sub-segments. Similarly, the second OTDR curve described above includes multiple second sub-segments, each being the smallest unit of granularity in the second OTDR curve. The distance corresponding to each second sub-segment on the horizontal axis is a second distance, which is the same as the first distance (because the first and second OTDR curves are obtained by the same fiber optic detection device for the same fiber). The second curve segment includes multiple second sub-segments. Therefore, replacing a first curve segment with a second curve segment is equivalent to replacing multiple first sub-segments with multiple second sub-segments. Since the first distances corresponding to multiple first sub-segments are the same as the second distances corresponding to multiple second sub-segments, this replacement allows for smooth splicing and avoids misalignment. The process of replacing the second curve segment with the first curve segment is similar and will not be elaborated here.

[0146] In summary, the fiber optic detection device provided in this application embodiment performs both phase modulation and corresponding phase demodulation, as well as intensity modulation and corresponding intensity demodulation. The accuracy of identification using phase modulation and intensity modulation varies for different events; using both phase modulation and intensity modulation can cover a variety of event identification scenarios. Therefore, the embodiments of this application provide more accurate event identification, stronger applicability, and greater flexibility.

[0147] The fiber optic detection device provided in the embodiments of this application has been described above. This application also provides a method for identifying events, which can be applied to the aforementioned fiber optic detection device. For example, it can be applied to the photoelectric detection module and processing module included in the aforementioned fiber optic detection device. Figure 18 As shown, the method includes the following steps 1801 and 1802.

[0148] Step 1801: Obtain electrical signals based on optical signals and return signals. The return signals are output by optical fiber based on optical pulse signals. The optical pulse signals are obtained by performing phase modulation and intensity modulation on optical signal segments in different time periods of the optical signal according to the encoded pulses.

[0149] Step 1802: Perform phase demodulation and intensity demodulation on the electrical signal segments in different time periods to obtain event signals. The event signals are used to identify events occurring in the optical fiber. The electrical signal segments correspond to the optical signal segments.

[0150] Optionally, step 1801 is executed by the photoelectric detection module, for example, by the computing unit included in the photoelectric detection module described above, the computing unit including but not limited to MCU or DSP chips. Step 1802 is executed by the processing module, for example, by the MCU or DSP chip used as the processing module described above.

[0151] In an exemplary embodiment, the event signal includes a first event signal and a second event signal. The first event signal is obtained by phase demodulation, and the second event signal is obtained by intensity demodulation. Alternatively, the event signal is obtained by combining the first event signal and the second event signal.

[0152] For example, performing phase demodulation and intensity demodulation on electrical signal segments within different time periods to obtain an event signal includes: performing phase demodulation on electrical signal segments within different time periods to obtain a first event signal; acquiring a first signal segment from the first event signal, wherein the power of the first signal segment is greater than or equal to a first power threshold; performing intensity demodulation on electrical signal segments within different time periods to obtain a second event signal; acquiring a second signal segment from the second event signal, wherein the power of the second signal segment is less than a second power threshold, and the second power threshold is less than or equal to the first power threshold; and merging the first signal segment and the second signal segment to obtain the event signal.

[0153] It should be understood that, Figure 18 The technical effects of the event identification method shown are the same as those of the fiber optic detection device described above, and will not be repeated here.

[0154] In an exemplary embodiment, this application also provides an OLT, which includes the fiber optic detection device described above, for example... Figures 4 to 7 , Figures 10 to 15 The fiber optic detection device shown.

[0155] In one example, this application embodiment also provides a chip including a processor, the processor being configured to retrieve and execute instructions stored in memory, causing a communication device on which the chip is mounted to perform... Figure 18 The method for identifying events is shown.

[0156] In another example, this application embodiment also provides another chip, which includes an input interface, an output interface, a processor, and a memory. The input interface, output interface, processor, and memory are connected via internal interconnection paths. The processor is used to execute code in the memory; when the code is executed, the communication device with the chip installed performs [operations / functions]. Figure 18 The method for identifying events is shown.

[0157] Optionally, the processor included in the chip may be, for example, an MCU or DSP chip as described above, but is not limited thereto.

[0158] In this application, the terms "first," "second," etc., are used to distinguish identical or similar items that have essentially the same function. It should be understood that there is no logical or temporal dependency between "first," "second," and "nth," nor does it limit the quantity or order of execution. It should also be understood that although the following description uses the terms "first," "second," etc., to describe various elements, these elements should not be limited by the terms. These terms are merely used to distinguish one element from another.

[0159] It should also be understood that, in the various embodiments of this application, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0160] In this application, the term "at least one" means one or more, and the term "multiple" means two or more. For example, multiple optical signal segments refer to two or more optical signal segments. The terms "system" and "network" are often used interchangeably in this document.

[0161] It should be understood that the terminology used in the description of the various examples herein is for the purpose of describing the particular examples only and is not intended to be limiting. As used in the description of the various examples and in the appended claims, the singular forms “a” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0162] It should also be understood that the terms “if” and “if” can be interpreted as meaning “when” or “upon”, or “in response to determination” or “in response to detection”. Similarly, depending on the context, the phrases “if determination…” or “if detection [the stated condition or event]” can be interpreted as meaning “when determination…”, or “in response to determination…”, or “when detection [the stated condition or event]” or “in response to detection [the stated condition or event]”.

[0163] The above description is merely an embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the protection scope of this application.

Claims

1. An optical fiber detection device, characterized in that, The fiber optic detection device includes a light source, an encoded pulse generation module, a modulation module, a photoelectric detection module, and a processing module. The light source and the encoded pulse generation module are respectively connected to the modulation module, and the light source and the processing module are respectively connected to the photoelectric detection module. The modulation module and the photoelectric detection module are also respectively connected to an optical fiber. The light source is used to output optical signals to the modulation module and the photoelectric detection module respectively; The encoded pulse generation module is used to output encoded pulses to the modulation module; The modulation module is used to perform phase modulation and intensity modulation on optical signal segments in different time periods of the optical signal according to the encoded pulse to obtain an optical pulse signal, and output the optical pulse signal to the optical fiber so that the optical fiber outputs a return signal; The photoelectric detection module is used to acquire an electrical signal based on the optical signal and the return signal, and output the electrical signal to the processing module. The processing module is used to perform phase demodulation and intensity demodulation on electrical signal segments at different time periods in the electrical signal to obtain event signals. The event signals are used to identify events occurring in the optical fiber, and the electrical signal segments correspond to the optical signal segments.

2. The optical fiber detection device according to claim 1, characterized in that, The encoded pulse includes a phase encoded pulse and an intensity encoded pulse; The coded pulse generation module is used to output the phase coded pulse to the modulation module during a first time period and to output the intensity coded pulse to the modulation module during a second time period. The modulation module is used to perform phase modulation on the optical signal segment in the first time period according to the phase encoding pulse to obtain a phase pulse signal, and to perform intensity modulation on the optical signal segment in the second time period according to the intensity encoding pulse to obtain an intensity pulse signal. The optical pulse signal includes the phase pulse signal and the intensity pulse signal.

3. The optical fiber detection device according to claim 2, characterized in that, The modulation module includes a phase modulation module and an intensity modulation module. The light source, the phase modulation module, and the intensity modulation module are sequentially connected to the optical fiber. The phase modulation module and the intensity modulation module are also respectively connected to the coded pulse generation module. The coded pulse also includes a first DC signal and a second DC signal. The encoded pulse generation module is configured to output the phase encoded pulse to the phase modulation module and output a first DC signal to the intensity modulation module during the first time period, and output the second DC signal to the phase modulation module and output the intensity encoded pulse to the intensity modulation module during the second time period; The phase modulation module is used to perform phase modulation on the optical signal segment within the first time period according to the phase encoding pulse to obtain the phase pulse signal; The intensity modulation module is used to transmit the phase pulse signal according to the first DC signal; The phase modulation module is used to transmit the optical signal segment within the second time period according to the second DC signal; The intensity modulation module is used to modulate the intensity of the optical signal segment in the second time period according to the intensity encoded pulse to obtain the intensity pulse signal.

4. The optical fiber detection device according to claim 2, characterized in that, The modulation module includes a phase modulation module and an intensity modulation module. The light source, the intensity modulation module, and the phase modulation module are sequentially connected to the optical fiber. The phase modulation module and the intensity modulation module are also respectively connected to the coded pulse generation module. The coded pulse also includes a first DC signal and a second DC signal. The encoded pulse generation module is configured to output the phase encoded pulse to the phase modulation module and output a first DC signal to the intensity modulation module during the first time period, and output the second DC signal to the phase modulation module and output the intensity encoded pulse to the intensity modulation module during the second time period; The intensity modulation module is used to transmit the optical signal segment within the first time period according to the first DC signal; The phase modulation module is used to perform phase modulation on the optical signal segment within the first time period according to the phase encoding pulse to obtain the phase pulse signal; The intensity modulation module is used to modulate the intensity of the optical signal segment in the second time period according to the intensity encoded pulse to obtain the intensity pulse signal; The phase modulation module is used to transmit the intensity pulse signal according to the second DC signal.

5. The optical fiber detection device according to any one of claims 1-4, characterized in that, The event signal includes a first event signal and a second event signal, wherein the first event signal is obtained by the phase demodulation and the second event signal is obtained by the intensity demodulation. Alternatively, the event signal can be obtained by merging the first event signal and the second event signal.

6. The optical fiber detection device according to claim 5, characterized in that, The processing module is used to obtain a first signal segment in the first event signal, wherein the power of the first signal segment is greater than or equal to a first power threshold. The processing module is used to acquire a second signal segment in the second event signal, wherein the power of the second signal segment is less than a second power threshold, and the second power threshold is less than or equal to the first power threshold; The processing module is used to merge the first signal segment and the second signal segment to obtain the event signal.

7. The optical fiber detection device according to any one of claims 1-6, characterized in that, The encoded pulse generation module includes a digital pulse generation module and a digital-to-analog conversion module, and the digital pulse generation module, the digital-to-analog conversion module and the modulation module are connected in sequence. The digital pulse generation module is used to generate coded pulses in digital form and output the coded pulses in digital form to the digital-to-analog conversion module; The digital-to-analog conversion module is used to convert the digital encoded pulse into an analog encoded pulse and output the analog encoded pulse to the modulation module.

8. The optical fiber detection device according to any one of claims 1-6, characterized in that, The encoded pulse generation module includes a timing control module and an analog pulse generation module, which are sequentially connected to the modulation module. The timing control module is used to generate timing control signals and output the timing control signals to the analog pulse generation module; The analog pulse generation module is used to generate an analog coded pulse according to the timing control signal and output the analog coded pulse to the modulation module.

9. The optical fiber detection device according to any one of claims 2-4, characterized in that, The ratio of the first quantity to the second quantity is the first proportion, where the first quantity is the number of phase-coded pulses output in the first time period, and the second quantity is the number of intensity-coded pulses output in the second time period. Alternatively, the ratio of the duration of the first time period to the duration of the second time period is a second ratio.

10. An optical line terminal, characterized in that, The optical line terminal includes the optical fiber detection device according to any one of claims 1-9.

11. A method for identifying events, characterized in that, The method includes: An electrical signal is obtained based on an optical signal and a return signal. The return signal is output by an optical fiber based on an optical pulse signal. The optical pulse signal is obtained by performing phase modulation and intensity modulation on optical signal segments in different time periods of the optical signal according to the encoded pulse. Phase demodulation and intensity demodulation are performed on electrical signal segments at different time periods to obtain event signals. The event signals are used to identify events occurring in the optical fiber, and the electrical signal segments correspond to the optical signal segments.

12. The method according to claim 11, characterized in that, The event signal includes a first event signal and a second event signal, wherein the first event signal is obtained by the phase demodulation and the second event signal is obtained by the intensity demodulation. Alternatively, the event signal can be obtained by merging the first event signal and the second event signal.

13. The method according to claim 12, characterized in that, The step of performing phase demodulation and intensity demodulation on electrical signal segments within different time periods to obtain event signals includes: Phase demodulation is performed on the electrical signal segments within the different time periods to obtain the first event signal; Obtain a first signal segment from the first event signal, wherein the power of the first signal segment is greater than or equal to a first power threshold; The electrical signal segments within the different time periods are demodulated to obtain the second event signal; Obtain a second signal segment from the second event signal, wherein the power of the second signal segment is less than a second power threshold, and the second power threshold is less than or equal to the first power threshold; The first signal segment and the second signal segment are combined to obtain the event signal.

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