Xpm crosstalk suppression method for Φ-otdr and mz-sagnac fusion system based on single pulse period local symmetry pairing

Abstract

The application discloses a Φ-OTDR and MZ-Sagnac fusion system XPM crosstalk suppression method based on single-pulse period local symmetry pairing, and is suitable for a single-fiber composite sensing system which integrates a Φ-OTDR module and a MZ-Sagnac interference module in the same sensing optical fiber through a wavelength division multiplexing mode. The method of the application obtains a pulse trigger signal and an interference output signal of the Φ-OTDR, synchronously segments the interference output signal according to a pulse repetition period, determines a local time window and a center position of the local time window affected by XPM crosstalk in each single-pulse period, then performs a weighted pairing operation on equidistant sampling points on both sides of the center, obtains a local recovery signal and an XPM crosstalk estimation component, and corrects a contaminated signal by using the local recovery signal, so as to realize XPM crosstalk suppression, improve the phase demodulation precision, disturbance positioning ability and event identification reliability of the composite sensing system.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing and signal processing technology, and in particular to an XPM crosstalk suppression method for a fusion system of Φ-OTDR and MZ-Sagnac based on single-pulse periodic local symmetric pairing. Background Technology

[0002] Optical time-domain reflectometry (OTDR) distributed fiber optic sensing technology leverages the dual transmission and sensing capabilities of optical fibers to achieve continuous sensing along the entire fiber length. It boasts advantages such as long monitoring distance, strong resistance to electromagnetic interference, and good environmental adaptability, making it widely applicable in perimeter security, pipeline monitoring, rail transit, and structural health monitoring. On the other hand, fiber optic sensing technology based on interferometric structures exhibits high phase sensitivity and good weak signal detection capabilities, enabling high-fidelity recovery of information from external vibrations or disturbances. In existing technologies, OTDR systems are typically used for distributed positioning, while interferometer systems are used for high-sensitivity dynamic signal detection, thus balancing monitoring distance, spatial positioning capability, and phase demodulation accuracy.

[0003] To balance distributed positioning capabilities with high-precision phase detection, current technologies often integrate a Φ-OTDR module and an MZ-Sagnac interferometer module into the same sensing fiber, constructing a single-fiber composite sensing system. However, in these systems, the Φ-OTDR module typically operates with high-power pulsed light, while the MZ-Sagnac interferometer module typically operates with continuous light. When these two types of optical signals propagate together in the same sensing fiber, cross-phase modulation (XPM) crosstalk is easily generated due to fiber nonlinearity. This crosstalk is superimposed on the interferometric output signal, leading to phase distortion, waveform distortion, positioning deviation, and decreased measurement stability, especially noticeable in long-distance monitoring and weak disturbance detection scenarios.

[0004] To mitigate the aforementioned effects, existing technologies typically employ global filtering, model compensation, pre- and post-stage signal correction, or post-processing methods based on statistical characteristics to suppress nonlinear crosstalk. While these methods can improve output quality to some extent, they usually rely on statistical modeling of the entire signal or require complex parameter estimation processes, resulting in issues such as insufficient real-time performance, high implementation complexity, and sensitivity to changes in operating conditions. Furthermore, directly using cross-cycle differential or global filtering methods may weaken slowly varying useful signals while suppressing XPM crosstalk, thereby affecting the fidelity recovery of the interferometric signal. Summary of the Invention

[0005] To address the cross-phase modulation crosstalk problem caused by the co-propagation of high-power Φ-OTDR pulsed light and interferometer continuous light in the same sensing fiber in existing Φ-OTDR and MZ-Sagnac single-fiber composite sensing systems, this invention proposes an XPM crosstalk suppression method for Φ-OTDR and MZ-Sagnac fusion systems based on single-pulse periodic local symmetrical pairing. By utilizing the synchronization relationship between the Φ-OTDR pulse triggering information and the MZ-Sagnac interferometric output signal, XPM crosstalk in the single-fiber composite sensing system is suppressed, thereby improving the measurement accuracy and operational stability of the composite sensing system.

[0006] This invention adopts the following technical solution: a method for XPM crosstalk suppression in a fusion system of Φ-OTDR and MZ-Sagnac based on single-pulse periodic local symmetric pairing, comprising the following steps:

[0007] S1. Construct a single-fiber composite sensing system, and integrate the Φ-OTDR module and the MZ-Sagnac interferometer module into the same sensing fiber through wavelength division multiplexing, and obtain the pulse trigger signal of the Φ-OTDR module and the output signal of the MZ-Sagnac interferometer module.

[0008] S2. Based on the repetition period of the pulse trigger signal, the output signal of the MZ-Sagnac interferometer module is synchronously segmented to obtain multiple single-pulse periodic signals;

[0009] S3. Determine the local time window affected by XPM crosstalk within each single pulse period signal, and determine the center position of the XPM crosstalk waveform within the local time window.

[0010] S4. Perform weighted pairing operations on the equidistant sampling points on both sides of the center position to obtain the local recovery signal and the XPM crosstalk estimation component.

[0011] S5. The contaminated signal within the local time window is corrected using the local recovery signal, and the corrected local signal is spliced ​​with the original signal outside the window to output the interference signal after suppressing XPM crosstalk.

[0012] S6. Perform subsequent phase demodulation, disturbance localization or event identification on the interference signal after suppressing XPM crosstalk to improve the reliability of the single-fiber composite sensing system in long-distance monitoring and weak disturbance detection scenarios.

[0013] The single-fiber composite sensing system includes: a Φ-OTDR module, an MZ-Sagnac interferometer module, a wavelength division multiplexer, a sensing fiber, a Faraday rotator, a photodetector, a data acquisition card, and a host computer. The method utilizes the synchronization relationship between the Φ-OTDR pulse trigger information and the MZ-Sagnac interferometer output signal to suppress XPM crosstalk in the single-fiber composite sensing system.

[0014] As a preferred embodiment, the Φ-OTDR module generates a probe light signal through a first laser, which is split into two paths through a first optical coupler. One of the paths, with 90% of the light split, is modulated by an acousto-optic modulator to form a pulsed light signal. Driven by an arbitrary waveform generator, the signal is amplified by an optical amplifier and input into a circulator, and then output to the first wavelength division multiplexer.

[0015] The output of the first wavelength division multiplexer is connected to the Faraday rotator mirror via the sensing fiber and the second wavelength division multiplexer in sequence. After the backscattered or reflected light in the sensing fiber returns, it is coupled with one of the 10% split beams by the circulator to the second optical coupler, outputting a periodic pulse detection signal and simultaneously outputting a pulse trigger signal to the first detector. The signal is collected by the data acquisition card and transmitted to the host computer.

[0016] As a preferred option, the MZ-Sagnac interferometer module generates a continuous light source through a second laser, which then enters a third optical coupler after passing through an optical isolator and splits into two paths. One path passes through a time-delay fiber and enters a fourth optical coupler, while the other path enters the fourth optical coupler directly.

[0017] After the two beams are coupled at the fourth optical coupler, they enter the shared sensing fiber through the first wavelength division multiplexer, propagate to the second wavelength division multiplexer and are reflected by the Faraday rotator, and then form interference at the third optical coupler. The output is an electrical signal containing the useful interference signal and the XPM crosstalk component, which is synchronously acquired by the second detector and the data acquisition card and transmitted to the host computer.

[0018] As a preferred embodiment, step S2 is specifically as follows:

[0019] S2-1. Time-align the electrical signal according to the start time and repetition period of the pulse trigger signal;

[0020] S2-2. Divide the time-aligned electrical signal into multiple single-pulse periodic signals to establish a one-to-one correspondence between each Φ-OTDR pulse and the corresponding XPM crosstalk waveform.

[0021] As a preferred embodiment, step S3 is specifically as follows:

[0022] S3-1. Within a single pulse cycle, determine the local time window affected by XPM crosstalk based on the pre-calibration results under conditions of no external disturbance, the online statistical results during operation, or the fixed time delay mapping relationship based on the pulse trigger time.

[0023] S3-2. Within the local time window, the center position of the XPM crosstalk waveform is determined using methods such as local extremum search, zero cross search, cross-correlation matching, or template matching.

[0024] S3-3. Using the center position as a reference, establish pairs of equidistant sampling points on both sides of the center for subsequent pairing operations.

[0025] As a preferred embodiment, steps S4 and S5 are as follows:

[0026] S4-1. Based on the interference output signal within a single pulse period, a weighted pairing operation is performed on the sampling points that are equidistant from the center position on both sides of the center position to obtain the local recovery signal;

[0027] S4-2. Perform a difference operation on the sampling points to obtain the XPM crosstalk estimation components;

[0028] S5-1. Replace the contaminated signal within the local time window with the local recovery signal;

[0029] S5-2. Use a smoothing fusion function to stitch the edge of the local time window with the original signal outside the window to reduce the distortion caused by abrupt boundary changes.

[0030] As a preferred embodiment, the interference output signal within the single pulse period is represented as follows: :

[0031] ;

[0032] in, For useful interference signals, For XPM crosstalk components, This is a noise component;

[0033] In step S4, around the center position Select sampling points that are equidistant from the center location The local recovery signal is obtained through the following expression:

[0034] ;

[0035] in, For the first The local recovery signal corresponding to each pairing point For paired weights, For the first The time offset of each pair of points relative to the center position.

[0036] As a preferred approach, while obtaining the local recovered signal, the crosstalk estimation component of XPM can also be obtained through differential operation to characterize the crosstalk intensity and distribution characteristics within the local time window. After completing the local correction, a smoothing fusion function is used to splice the original signal at the edge of the local time window with the signal outside the window to reduce abrupt distortion at the boundary.

[0037] As a preferred option, before performing the weighted pairing operation, the central symmetry of the signal within the local time window is first determined; if the symmetry index within the local time window is lower than a preset threshold, the pairing weight is reduced, the local time window is shortened, or the correction process for the current single pulse cycle is skipped.

[0038] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0039] 1. This invention addresses the XPM crosstalk problem in Φ-OTDR and MZ-Sagnac single-fiber composite sensing systems. It directly utilizes the local time-domain structural characteristics of the crosstalk waveform within a single pulse period for correction, without relying on global statistical filtering or complex model compensation. The method has a clear implementation path and is relatively simple to implement in engineering.

[0040] 2. Based on pulse synchronization segmentation, local window extraction, center positioning, and weighted pairing of equidistant sampling points, this invention only processes the local area affected by XPM crosstalk, which can reduce the influence on useful interference signals outside the window and thus improve signal fidelity.

[0041] 3. By restoring and correcting locally contaminated signals, this invention can effectively reduce phase distortion, waveform distortion and positioning deviation caused by XPM crosstalk, thereby improving the measurement accuracy and stability of the composite sensing system in long-distance monitoring, weak disturbance detection and event recognition scenarios.

[0042] 4. In this invention, the pairing weights, local time windows, and center positions can all be adjusted according to the actual system state, which has good adaptability and scalability and is suitable for XPM crosstalk suppression in single-fiber composite sensing systems under different working conditions. Attached Figure Description

[0043] Figure 1 This is a structural diagram of the Φ-OTDR and MZ-Sagnac fusion system of the present invention.

[0044] Figure 2 This is a flowchart of the XPM crosstalk suppression method for the Φ-OTDR and MZ-Sagnac fusion system of the present invention.

[0045] Figure 3This is a schematic diagram of the original signal and a single-cycle local magnification of multiple pulse cycles affected by XPM in an embodiment of the present invention.

[0046] Figure 4 This is a comparison diagram of the local waveforms of the interference output signal before and after XPM suppression in an embodiment of the present invention.

[0047] Figure 5 This is a comparison chart of demodulation results using traditional processing methods and the XPM crosstalk suppression method of this invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the application will be further described in detail below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments involved in this invention. All non-innovative embodiments based on these embodiments by other researchers in the art are within the protection scope of this invention. Furthermore, the step numbers in the embodiments of this invention are only set for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0049] In one embodiment of the present invention, an XPM crosstalk suppression method for a Φ-OTDR and MZ-Sagnac fusion system based on single-pulse periodic local symmetric pairing is provided. This method is applicable to single-fiber composite sensing systems that integrate the Φ-OTDR module and the MZ-Sagnac interferometer module in the same sensing fiber through wavelength division multiplexing.

[0050] Specifically, the structure of a single-fiber composite sensing system, such as Figure 1 As shown, it includes: a first laser, a first optical coupler, an acousto-optic modulator, an optical amplifier, a circulator, a first detector, a second optical coupler, a second laser, an optical isolator, a third optical coupler, a delay fiber, a fourth optical coupler, a second detector, a wavelength division multiplexer 1, a sensing fiber, a wavelength division multiplexer 2, a Faraday rotator, an arbitrary waveform generator, a data acquisition card, and a host computer.

[0051] In this embodiment, the first laser is a narrow-linewidth laser with a wavelength of 1550nm, used to generate probe light. The optical signal output from the first laser is split into two paths by a first optical coupler. One path, with 90% of the light split, is modulated by an acousto-optic modulator to form a pulsed optical signal. Driven by an arbitrary waveform generator, the pulse width is set to 1μs and the repetition frequency to 12.5kHz. After being amplified by an optical amplifier, the signal is input to a circulator. The output of the circulator is connected to one path of the corresponding narrow-linewidth laser wavelength of wavelength division multiplexer 1. The output of wavelength division multiplexer 1 is connected to a sensing fiber. The end of the sensing fiber is connected to the input of wavelength division multiplexer 2. Finally, one path of the second laser wavelength of wavelength division multiplexer 2 is connected to a Faraday rotator. After the backscattered or reflected light in the sensing fiber returns, it is split by 10% by the circulator and the first optical coupler and output to the second optical coupler. The output of the second optical coupler is then sent to the first detector and acquired by a data acquisition card for synchronous triggering and status acquisition of the Φ-OTDR module.

[0052] In this embodiment, the second laser is a continuous light source with a wavelength of 1563 nm, used to construct the MZ-Sagnac interferometer module. The continuous light output from the second laser enters the third optical coupler after passing through an optical isolator, where it is split into two paths. One path passes through a time-delay fiber, and the other path directly enters the fourth optical coupler. The two paths are coupled at the fourth optical coupler and then coupled through wavelength division multiplexer 1 into the sensing fiber shared with the Φ-OTDR module. The light then propagates through the sensing fiber to wavelength division multiplexer 2, where it is reflected by wavelength division multiplexer 2 and a Faraday rotator mirror, forming interference at the third optical coupler. This interference is received by the second detector and transmitted to the data acquisition card, and finally sent to the host computer for further processing.

[0053] In the aforementioned system, the Φ-OTDR module operates using high-power pulsed light, while the MZ-Sagnac interferometer module operates using continuous light. When the pulsed light and continuous light propagate together in the same sensing fiber, due to the Kerr nonlinearity of the fiber, the pulsed light will induce cross-phase modulation on the continuous light, thereby introducing XPM crosstalk synchronized with the pulse period into the interferometric output signal. This crosstalk will be superimposed on the useful interferometric signal, leading to phase distortion, waveform distortion, and increased subsequent disturbance positioning errors.

[0054] To suppress this effect, this embodiment proposes an XPM crosstalk suppression method based on a single-pulse periodic local time window and centrally symmetric pairing, the process of which is as follows: Figure 2 As shown.

[0055] First, a synchronization control signal is output from an arbitrary waveform generator, serving as the trigger reference for pulse transmission from the Φ-OTDR module and simultaneously as the time synchronization reference for processing the interferometric output signal. The host computer synchronously acquires the pulse trigger signal from the Φ-OTDR module and the output signal from the MZ-Sagnac interferometer module via a data acquisition card.

[0056] Subsequently, based on the start time and repetition period of the pulse trigger signal, the acquired interference output signal is time-aligned and divided into multiple single-pulse periodic signals, thereby establishing a one-to-one correspondence between each Φ-OTDR pulse and the corresponding XPM crosstalk waveform.

[0057] Within a single pulse cycle, this embodiment first determines the local time window affected by XPM. As a preferred approach, multiple pulse cycles of interference output signals can be pre-acquired under conditions of no external disturbance. By statistically analyzing the local waveform characteristics at the same relative moment, the time interval in which XPM crosstalk stably occurs can be determined, and this time interval can be used as the local contamination window. Alternatively, the location of the local contamination window can be directly determined based on the fixed time delay relationship between the Φ-OTDR pulse trigger time and the local abnormal waveform in the interference output.

[0058] After determining the local contamination window, it is necessary to further determine the center position of the XPM crosstalk waveform. As a preferred approach, the center position of the crosstalk waveform within the local time window can be obtained using methods such as local extremum search, zero-crossing search, cross-correlation matching, or template matching. .

[0059] In this embodiment, the original signal affected by XPM for multiple pulse periods and the local amplification result of a single period are as follows: Figure 3 As shown. Figure 3 (a) in the figure shows the original signal diagram affected by XPM over multiple cycles. Figure 3 (b) in the diagram shows the local pollution window and centrally symmetrical pairing of XPM within a single cycle. It can be seen that, in the context of... Within the local time window centered on this point, the XPM crosstalk waveform typically exhibits approximately centrosymmetric characteristics on both sides. Therefore, several sets of equidistant sampling points can be established around this central location. ,in, For the first The time offset of each sampling point relative to the center position.

[0060] Let the interference output signal within a single pulse period be expressed as:

[0061] ;

[0062] in, For useful interference signals, For XPM crosstalk components, This represents the noise component. It is based on the approximate centrosymmetric characteristics of the XPM crosstalk waveform within the local time window.

[0063] Then, a weighted pairing operation is performed on the equidistant sampling points on both sides of the center position to obtain the local recovered signal. As a preferred scheme, its expression is:

[0064] ;

[0065] in, For the first The local recovery signal corresponding to each pairing point For pairing weights.

[0066] Specifically, the pairing weights It can be determined by least squares estimation, adaptive iterative update or pre-calibration lookup table, or it can be selected based on the smoothness, symmetry or size of local residuals of the local recovered signal.

[0067] While obtaining the locally recovered signal, the XPM crosstalk estimation component can also be obtained through differential operations, and its expression is:

[0068] ;

[0069] in, For the first Each pairing point corresponds to an XPM crosstalk estimation component. Using these XPM crosstalk estimation components, the strength of crosstalk within the current single-pulse cycle can be further evaluated, and adaptive adjustments can be made to the pairing weights, the width of the local time window, or whether correction is performed in the current cycle.

[0070] After completing the above weighted pairing operation, the original contaminated signal within the local time window is replaced with the local recovered signal, and then spliced ​​with the original signal outside the window to obtain the interference output signal after suppressing XPM crosstalk.

[0071] To reduce abrupt distortion at the boundaries of local time windows, a preferred approach is to introduce a smoothing fusion function at the edges of the local time window to enable a smooth transition between the corrected signal inside the window and the original signal outside the window.

[0072] In practical implementation, the central symmetry within the local time window can be determined before pairing operations. If the symmetry index of the signal within the current local time window is lower than a preset threshold, the pairing weight can be reduced, the local time window can be shortened, or the correction process for the current single pulse cycle can be skipped to avoid introducing additional distortion under non-ideal conditions.

[0073] Furthermore, a vibration disturbance with a known frequency of 10kHz and an amplitude of 0.25 is applied at a certain position of the sensing fiber, and the output results of the conventional processing method and the method described in this invention are compared.

[0074] The comparison results of the local waveforms of the interference output signal before and after XPM suppression are as follows: Figure 4 As shown, Figure 4 (a) in the figure is the local waveform before suppression. Figure 4 (b) in the figure shows the local waveform after suppression. It can be seen that after using the method of the present invention, the original local abnormal waveform is significantly corrected, the local phase disturbance is reduced, and the smoothness and consistency of the interference output signal are improved.

[0075] Furthermore, the demodulation results obtained by using the traditional processing method and the method of this invention are compared, such as... Figure 5 As shown, Figure 5 (a) in the figure represents the result of the traditional processing method; Figure 5 Figure (b) shows the results of the method of the present invention. It can be seen that after adopting the method of the present invention, the abnormal fluctuations and misjudgments in the demodulation results are significantly reduced, and the disturbance location identification is more stable. This indicates that the XPM crosstalk suppression method proposed in this invention can effectively reduce the impact of XPM crosstalk on phase demodulation, disturbance location and event identification, thereby improving the measurement accuracy and stability of the Φ-OTDR and MZ-Sagnac single-fiber composite sensing system.

[0076] In summary, the method of this invention utilizes the synchronization relationship between the Φ-OTDR pulse trigger information and the MZ-Sagnac interferometric output signal to suppress XPM crosstalk in a single-fiber composite sensing system. Specifically, the interferometric output signal is periodically segmented according to the Φ-OTDR pulse repetition period. Within each single pulse period, the local time window affected by XPM crosstalk and its center position are determined. Subsequently, weighted pairing operations are performed on equidistant sampling points on both sides of the center to obtain the local recovered signal and the estimated XPM crosstalk component. The local recovered signal is then used to correct the contaminated signal, thereby reducing the impact of XPM crosstalk on the interferometric output signal and effectively improving the phase demodulation accuracy and event recognition reliability of the composite sensing system.

[0077] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for XPM crosstalk suppression in a fusion system of Φ-OTDR and MZ-Sagnac based on single-pulse periodic local symmetric pairing, characterized in that, Includes the following steps: S1. Construct a single-fiber composite sensing system, and integrate the Φ-OTDR module and the MZ-Sagnac interferometer module into the same sensing fiber through wavelength division multiplexing, and obtain the pulse trigger signal of the Φ-OTDR module and the output signal of the MZ-Sagnac interferometer module. S2. Based on the repetition period of the pulse trigger signal, the output signal of the MZ-Sagnac interferometer module is synchronously segmented to obtain multiple single-pulse periodic signals; S3. Determine the local time window affected by XPM crosstalk within each single pulse period signal, and determine the center position of the XPM crosstalk waveform within the local time window. S4. Perform weighted pairing operations on the equidistant sampling points on both sides of the center position to obtain the local recovery signal and the XPM crosstalk estimation component. S5. The contaminated signal within the local time window is corrected using the local recovery signal, and the corrected local signal is spliced ​​with the original signal outside the window to output the interference signal after suppressing XPM crosstalk. S6. Perform subsequent phase demodulation, disturbance localization or event identification on the interference signal after suppressing XPM crosstalk to improve the reliability of the single-fiber composite sensing system in long-distance monitoring and weak disturbance detection scenarios.

2. The XPM crosstalk suppression method for the Φ-OTDR and MZ-Sagnac fusion system according to claim 1, characterized in that, In step S1, the Φ-OTDR module generates a probe light signal through the first laser, which is split into two paths through the first optical coupler. One path, with 90% of the light split, is modulated by an acousto-optic modulator to form a pulsed light signal. Driven by an arbitrary waveform generator, the signal is amplified by an optical amplifier and input into a circulator, and then output to the first wavelength division multiplexer. The output of the first wavelength division multiplexer is connected to the Faraday rotator mirror via the sensing fiber and the second wavelength division multiplexer in sequence. After the backscattered or reflected light in the sensing fiber returns, it is coupled with one of the 10% split beams by the circulator to the second optical coupler, outputting a periodic pulse detection signal and simultaneously outputting a pulse trigger signal to the first detector, which is then acquired by the data acquisition card.

3. The XPM crosstalk suppression method for the Φ-OTDR and MZ-Sagnac fusion system according to claim 1, characterized in that, In step S1, the MZ-Sagnac interferometer module generates a continuous light source through the second laser, which then enters the third optical coupler after passing through the optical isolator and splits into two paths. One path passes through the delay fiber and enters the fourth optical coupler, while the other path directly enters the fourth optical coupler. After the two beams are coupled at the fourth optical coupler, they enter the shared sensing fiber through the first wavelength division multiplexer, propagate to the second wavelength division multiplexer and are reflected by the Faraday rotator, and then form interference at the third optical coupler. The output is an electrical signal containing the useful interference signal and the XPM crosstalk component, which is synchronously acquired by the second detector and the data acquisition card.

4. The XPM crosstalk suppression method for the Φ-OTDR and MZ-Sagnac fusion system according to claim 1, characterized in that, Step S2 is as follows: S2-1. Time-align the electrical signal according to the start time and repetition period of the pulse trigger signal; S2-2. Divide the time-aligned electrical signal into multiple single-pulse periodic signals to establish a one-to-one correspondence between each Φ-OTDR pulse and the corresponding XPM crosstalk waveform.

5. The XPM crosstalk suppression method for the Φ-OTDR and MZ-Sagnac fusion system according to claim 4, characterized in that, The specific steps in S3 are as follows: S3-1. Within a single pulse period, determine the local time window affected by XPM crosstalk based on the pre-calibration results, online statistical results, or fixed time delay mapping relationship. S3-2. Within the local time window, the center position of the XPM crosstalk waveform is determined using methods such as local extremum search, zero cross search, cross-correlation matching, or template matching. S3-3. Using the center position as a reference, establish pairs of equidistant sampling points on both sides of the center for subsequent pairing operations.

6. The XPM crosstalk suppression method for the Φ-OTDR and MZ-Sagnac fusion system according to claim 5, characterized in that, Steps S4 and S5 are as follows: S4-1. Based on the interference output signal within a single pulse period, a weighted pairing operation is performed on the sampling points that are equidistant from the center position on both sides of the center position to obtain the local recovery signal; S4-2. Perform a difference operation on the sampling points to obtain the XPM crosstalk estimation components; S5-1. Replace the contaminated signal within the local time window with the local recovery signal; S5-2. Use a smoothing fusion function to stitch the edge of the local time window with the original signal outside the window to reduce the distortion caused by abrupt boundary changes.

7. The XPM crosstalk suppression method for the Φ-OTDR and MZ-Sagnac fusion system according to claim 6, characterized in that, The interference output signal within the single pulse period is represented as: : ； in, For useful interference signals, For XPM crosstalk components, This is a noise component; In step S4, around the center position Select sampling points that are equidistant from the center location The local recovery signal is obtained through the following expression: ； in, For the first The local recovery signal corresponding to each pairing point For paired weights, For the first The time offset of each pair of points relative to the center position.

8. The XPM crosstalk suppression method for the Φ-OTDR and MZ-Sagnac fusion system according to claim 7, characterized in that, The XPM crosstalk estimation component is obtained through the following difference expression: ； in, For the first The XPM crosstalk estimation components corresponding to each pairing point.

9. The XPM crosstalk suppression method for the Φ-OTDR and MZ-Sagnac fusion system according to claim 7, characterized in that, The pairing weight The selection can be based on the smoothness, symmetry, or size of the local residual of the recovered signal within the local time window, or determined by at least one method such as least squares estimation, adaptive iterative update, or pre-calibration lookup table.

10. The XPM crosstalk suppression method for the Φ-OTDR and MZ-Sagnac fusion system according to claim 7, characterized in that, Before performing the weighted pairing operation, the central symmetry of the signal within the local time window is determined. If the symmetry index within the local time window is lower than the preset threshold, the pairing weight is reduced, the local time window is shortened, or the correction process for the current single pulse cycle is skipped.

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