Optical fiber DAS phase demodulation method and demodulation device

Abstract

The invention provides an optical fiber DAS phase demodulation method and demodulation device. The demodulation method comprises the following steps: S1, acquiring a digital signal of a sensing optical fiber under each pulse signal; s2, after sub-band extraction and matched filtering are carried out on the digital signal under each pulse signal and the digital signal under the pulse signal at a preset interval from the digital signal, adjacent differential rotation vector summation processing is carried out, and a complex signal is obtained; s3, solving a phase angle for each complex signal, and performing phase angle expansion to obtain a phase signal; s4, performing spatial differential processing on each phase signal to obtain a phase demodulation signal; s5, according to a preset optical fiber sampling position, extracting a sampling point corresponding to the optical fiber sampling position in each phase demodulation signal to obtain a vibration signal; windowing processing, FFT conversion, frequency domain compensation, IFFT conversion and windowing processing are sequentially carried out on the vibration signal, and a result is output. Accumulated errors can be eliminated, and a complete frequency response range can be reserved.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing technology, and in particular to an optical fiber DAS phase demodulation method and a demodulation device. Background Art

[0002] OTDR technology, also known as optical time domain reflectometry, can obtain sensing information along the optical fiber based on the flight time of light in the optical fiber. When the phase of the backward Rayleigh scattered signal is used for demodulation, it is a phase-sensitive OTDR, namely the Φ-OTDR system, also known as the DAS system. The DAS system sends a detection pulse signal to the sensing optical fiber at a fixed period. The backward Rayleigh scattered light signal at each point along the optical fiber is received at the receiving end of the DAS system. By performing phase demodulation on these signals, the vibration distribution along the optical fiber can be dynamically demodulated.

[0003] The backward Rayleigh scattered light signal received under the pulse signal emitted by the DAS system will have relatively strong coherent fading noise, and the influence of coherent fading is generally eliminated by the method of rotating vector summation. There are currently two methods for rotating vector summation: 1. Select a reference signal curve, and then all collected signal curves need to be subtracted from this reference signal curve, but the reference signal curve will be affected by the stability of the light source and the optical path. The better the stability of the light source and the optical path, the better the demodulation result. Once there is a problem with the selection of the reference signal curve, all demodulation results will have problems, and there will be cumulative errors that are difficult to eliminate; 2. Select the collected adjacent signal curves for subtraction, which is equivalent to a first-order differential processing of the detection signal. Although it can eliminate the influence of cumulative errors, its effect is equivalent to a high-pass filter. After signal processing, the useful low-frequency signal will be greatly suppressed, and the frequency response range of the demodulation will be limited.

[0004] Therefore, an improved optical fiber DAS phase demodulation method and demodulation device are urgently needed. Summary of the invention

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a fiber DAS phase demodulation method and a demodulation device, which can eliminate the cumulative error and retain the complete frequency response range.

[0006] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0007] In a first aspect, the present invention provides a method for phase demodulation of an optical fiber DAS, comprising the following steps:

[0008] S1, collecting digital signals of the sensing optical fiber under each pulse signal emitted by the DAS system;

[0009] S2, extracting sub-bands and matching filters on the digital signal under each pulse signal and the digital signal under the pulse signal at a preset interval, and then performing adjacent differential rotation vector summation processing to obtain a complex signal; wherein the preset interval is an integer multiple of the pulse signal transmission interval;

[0010] S3, performing arctan operation on each complex signal to solve the phase angle, and performing phase angle expansion to obtain the phase signal of the sensing optical fiber under each pulse;

[0011] S4, performing spatial differential processing on each phase signal to obtain a phase demodulation signal of the sensing optical fiber under each pulse;

[0012] S5. According to the preset optical fiber sampling position, extract the sampling points corresponding to the optical fiber sampling position in each phase demodulation signal, arrange all the sampling points according to the sampling time, and obtain the vibration signal of the optical fiber sampling position; perform windowing and FFT transformation on the vibration signal in turn, and then perform low-frequency frequency domain compensation on the vibration signal according to the preset frequency domain compensation coefficient, and then perform IFFT transformation and windowing on the vibration signal after frequency domain compensation in turn, and output the result.

[0013] Optionally, the pulse signal transmitted by the DAS system is a single-frequency signal or a swept-frequency signal.

[0014] Optionally, S2 includes: using the intra-pulse frequency division method to divide the digital signal under each pulse into a preset number of signals of different frequency bands, performing first-order differential processing on the different frequency band signals under each pulse signal and the corresponding frequency band signals of the pulse signal at a preset interval therefrom, obtaining the first-order differential result corresponding to each pulse signal, adding all the first-order differential results corresponding to each pulse signal, and obtaining the complex signal of the sensing optical fiber under each pulse.

[0015] Optionally, in S1, two paths of backward Rayleigh scattered light signals of the sensing optical fiber under each pulse signal emitted by the DAS system are collected, and the two paths of backward Rayleigh scattered light signals are converted into two paths of digital signals.

[0016] Optionally, the digital signal under each pulse is divided into a preset number of signals of different frequency bands using an intra-pulse frequency division method, including:

[0017] The two digital signals collected by the sensing optical fiber under each pulse signal emitted by the DAS system are X-channel digital signal DATA_X_M and Y-channel digital signal DATA_Y_M;

[0018] Copy DATA_X_M to obtain DATA_X_S; copy DATA_Y_M to obtain DATA_Y_S;

[0019] Input DATA_X_M, DATA_X_S, DATA_Y_M, and DATA_Y_S into their respective corresponding frequency band division links to obtain different frequency band signals corresponding to DATA_X_M, different frequency band signals corresponding to DATA_X_S, different frequency band signals corresponding to DATA_Y_M, and different frequency band signals corresponding to DATA_Y_S;

[0020] Add the corresponding frequency band signals in DATA_X_M and DATA_X_S, add the corresponding frequency band signals in DATA_Y_M and DATA_Y_S, and output different frequency band signals of the digital signal under each pulse;

[0021] Among them, the frequency band division link includes at least two sub-band links set in parallel, and the frequency domain coefficients of at least two sub-band links are different from each other; the signal is input into the sub-band link, the signal is sequentially subjected to windowing processing and FFT transformation, and then the signal is subjected to frequency band extraction according to the pre-set sub-band frequency domain coefficients, and then the signal after frequency band extraction is sequentially subjected to IFFT transformation and windowing processing, and the result is output.

[0022] Optionally, the preset interval is a pulse signal transmission interval.

[0023] Optionally, performing first-order difference processing on different frequency band signals under each pulse signal and corresponding frequency band signals of the pulse signal at a preset interval therefrom to obtain a first-order difference result corresponding to each pulse signal includes:

[0024] Different frequency band signals under the pulse signal are alternately stored in the first first-in-first-out memory and the second first-in-first-out memory according to the transmission order of the pulse signal;

[0025] The different frequency band signals under the current pulse signal are conjugated and sent to the first first-in-first-out memory and the complex multiplier. At the same time, the different frequency band signals under the previous pulse signal are read from the second first-in-first-out memory and sent to the complex multiplier. The corresponding frequency band signals in the two pulse signals are multiplied and output in the complex multiplier to obtain the first-order difference result corresponding to the current pulse signal; or, the different frequency band signals under the current pulse signal are conjugated and sent to the second first-in-first-out memory and the complex multiplier. At the same time, the different frequency band signals under the previous pulse signal are read from the first first-in-first-out memory and sent to the complex multiplier. The corresponding frequency band signals in the two pulse signals are multiplied and output in the complex multiplier to obtain the first-order difference result corresponding to the current pulse signal.

[0026] Optionally, in S4, based on a preset spatial differential distance, a difference is taken between two sampling points separated by a spatial differential distance in each phase signal to obtain a phase demodulation signal of the sensing optical fiber under each pulse.

[0027] Optionally, in S5, a sine window, a rectangular window, a Hanning window or a Hamming window is used to perform windowing processing on the vibration signal.

[0028] In a second aspect, the present invention provides an optical fiber DAS phase demodulation device, comprising a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program stored in the memory, the steps of the optical fiber DAS phase demodulation method as described above are implemented.

[0029] The beneficial effects of the present invention are:

[0030] The optical fiber DAS phase demodulation method and demodulation device provided by the present invention use two adjacent pulse detection signals as references to perform rotating vector summation, which can eliminate cumulative errors, and after the rotating vector summation and after the phase demodulation is completed, a frequency domain filter is introduced into the demodulation result of the sampling position using short-time Fourier change to restore the suppressed low-frequency signal, thereby realizing wide-bandwidth real-time detection of extremely low-frequency to high-frequency signals and improving the accuracy and stability of signal processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic flow chart of a method for optical fiber DAS phase demodulation according to a specific embodiment of the present invention;

[0032] Figure 2 Schematic diagram of a process of dividing a digital signal into frequency bands according to a specific embodiment of the present invention, wherein Segk(n) is a window function, and G(n) is a sub-band frequency domain coefficient;

[0033] Figure 3 A schematic diagram of a process of performing first-order difference on a digital signal according to a specific embodiment of the present invention;

[0034] Figure 4 A schematic diagram of phase signals of a sensing optical fiber under three pulses according to a specific embodiment of the present invention;

[0035] Figure 5 For Figure 4 The phase signal in the sensor is spatially differentially processed to obtain a schematic diagram of the phase demodulation signal of the sensing optical fiber under each pulse;

[0036] Figure 6 Schematic diagram of the process of frequency domain compensation for vibration signals according to a specific embodiment of the present invention, wherein Segk(n) is a window function and H(n) is a frequency domain compensation coefficient. DETAILED DESCRIPTION

[0037] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0038] like Figure 1 As shown, the present invention provides a fiber DAS phase demodulation method. The fiber DAS phase demodulation method comprises the following steps:

[0039] S1. Collect the digital signal of the sensing optical fiber under each pulse signal emitted by the DAS system.

[0040] The pulse signal transmitted by the DAS system is a single-frequency signal or a swept-frequency signal.

[0041] As an example, in a DAS system, a fixed-period swept-frequency pulse signal is used to drive an acousto-optic modulator to generate a fixed-period swept-frequency pulse optical signal in the optical path. The backward Rayleigh scattered optical signal that passes through the sensing optical fiber and returns through the circulator is also swept-frequency, and the electrical signal obtained by the photodetector is also swept-frequency. The conversion of the electrical signal into a digital signal through the analog-to-digital converter ADC is also swept-frequency. For example: the length of the received return optical pulse is 100us. Taking a 250Msps ADC as an example, the signal length that needs to be processed under one pulse signal is 25,000 points.

[0042] In order to improve the accuracy of subsequent signal processing, preferably, in the DAS system, two photodetectors are used to collect two backward Rayleigh scattered light signals of the sensing optical fiber under each pulse signal emitted by the DAS system, and the two backward Rayleigh scattered light signals are converted into two digital signals through ADC, which are respectively recorded as X-channel digital signal DATA_X_M and Y-channel digital signal DATA_Y_M.

[0043] S2. After sub-band extraction and matched filtering of the digital signal under each pulse signal and the digital signal under the pulse signal at a preset interval, adjacent differential rotation vector summation processing is performed to obtain a complex signal; wherein the preset interval is an integer multiple of the pulse signal transmission interval.

[0044] Preferably, the digital signal under each pulse is divided into a preset number of signals of different frequency bands using the intra-pulse frequency division method, and the different frequency band signals under each pulse signal are subjected to first-order differential processing with the corresponding frequency band signals of the pulse signal at a preset interval therefrom to obtain the first-order differential result corresponding to each pulse signal, and all the first-order differential results corresponding to each pulse signal are added together to obtain the complex signal of the sensing optical fiber under each pulse.

[0045] Further preferably, the digital signal under each pulse is divided into a preset number of signals of different frequency bands using an intra-pulse frequency division method, including:

[0046] Copy DATA_X_M to obtain DATA_X_S; copy DATA_Y_M to obtain DATA_Y_S;

[0047] Input DATA_X_M, DATA_X_S, DATA_Y_M, and DATA_Y_S into their respective corresponding frequency band division links, and obtain different frequency band signals corresponding to DATA_X_M, different frequency band signals corresponding to DATA_X_S, different frequency band signals corresponding to DATA_Y_M, and different frequency band signals corresponding to DATA_Y_S; add the corresponding frequency band signals in DATA_X_M and DATA_X_S, and add the corresponding frequency band signals in DATA_Y_M and DATA_Y_S, and output different frequency band signals of two digital signals under each pulse;

[0048] The frequency band division link includes at least two sub-band links arranged in parallel, and the frequency domain coefficients of at least two sub-band links are different from each other; Figure 2 As shown, the signal is input into the sub-band link, the signal is subjected to windowing processing and FFT transformation in sequence, and then the signal is subjected to frequency band extraction according to the pre-set sub-band frequency domain coefficients, and then the signal after frequency band extraction is subjected to IFFT transformation and windowing processing in sequence, and the result is output.

[0049] The method described above is used to divide the frequency band of the pulse signal, which mostly involves only multiplication and addition operations, with relatively small computing resources. It is suitable for deployment on FPGA and ZYNQ platforms, which helps to reduce system costs.

[0050] As an example, the frequency band division link includes two sub-band links set in parallel. DATA_X_M is input into its corresponding frequency band division link, that is, DATA_X_M is input into two sub-band links in parallel. In the first sub-band link, DATA_X_M is sequentially subjected to windowing processing and FFT transformation, and then multiplied by the frequency domain coefficient of sub-band 1 to extract the signal, and then the signal after the frequency band extraction is sequentially subjected to IFFT transformation and windowing processing, and the complex signal of sub-band 1 is output. In the second sub-band link, DATA_X_M is sequentially subjected to windowing processing and FFT transformation, and then multiplied by the frequency domain coefficient of sub-band 2 to extract the signal, and then the signal after the frequency band extraction is sequentially subjected to IFFT transformation and windowing processing, and the complex signal of sub-band 2 is output. The process of DATA_X_S inputting its corresponding frequency band division link is similar to the process of DATA_X_M inputting its corresponding frequency band division link, and will not be repeated here. Subband 1 signals in DATA_X_M and DATA_X_S are added, and subband 2 signals in DATA_Y_M and DATA_Y_S are added, and the output X-channel signal is subjected to pulse compression to obtain a total of 2 complex signals, which respectively represent two parallel signals with different frequency components extracted from the original signal (X-channel signal). Similarly, the Y-channel signal is processed as above, and the output Y-channel signal is subjected to pulse compression to obtain a total of 2 complex signals, which respectively represent two parallel signals with different frequency components extracted from the original signal (Y-channel signal).

[0051] It should be noted that the above division of the digital signal into two frequency bands is only an example, and if computing resources (if implemented in FPGA, FPGA resources) allow, it is also possible to divide the digital signal into three or four frequency bands.

[0052] Preferably, the preset interval is a pulse signal transmission interval, so as to further reduce the occupation of computing resources.

[0053] Preferably, the first-order difference processing is performed on the different frequency band signals under each pulse signal and the corresponding frequency band signals of the pulse signal at a preset interval therefrom to obtain the first-order difference result corresponding to each pulse signal, including: the different frequency band signals under the pulse signal are alternately stored in the first first-in-first-out memory and the second first-in-first-out memory according to the transmission order of the pulse signal;

[0054] like Figure 3As shown, the different frequency band signals under the current pulse signal are conjugated and sent to the first first-in-first-out memory (FIFO1) and the complex multiplier, and the different frequency band signals under the previous pulse signal are read from the second first-in-first-out memory (FIFO2) and sent to the complex multiplier, and the corresponding frequency band signals in the two pulse signals are multiplied and output in the complex multiplier to obtain the first-order difference result corresponding to the current pulse signal; or, the different frequency band signals under the current pulse signal are conjugated and sent to the second first-in-first-out memory (FIFO2) and the complex multiplier, and the different frequency band signals under the previous pulse signal are read from the first first-in-first-out memory (FIFO1) and sent to the complex multiplier, and the corresponding frequency band signals in the two pulse signals are multiplied and output in the complex multiplier to obtain the first-order difference result corresponding to the current pulse signal. In this way, in the process of summing adjacent differential rotation vectors, most of them only involve multiplication and addition operations, and the computing resources are small, which is suitable for deployment on FPGA and ZYNQ platforms, thereby helping to reduce system costs.

[0055] S3. Perform arctan operation on each complex signal to solve the phase angle, and perform phase angle expansion to obtain the phase signal of the sensing optical fiber under each pulse.

[0056] As an example, the phase signal of the sensing fiber under three pulses is as follows: Figure 4 shown.

[0057] S4. Perform spatial differential processing on each phase signal to obtain a phase demodulation signal of the sensing optical fiber under each pulse.

[0058] The phase signal of the sensing optical fiber obtained in S3 under each pulse cannot well reflect the phase change, so spatial differential processing is performed on each phase signal.

[0059] Specifically, according to a preset spatial differential distance, a difference is made between two sampling points separated by the spatial differential distance in each phase signal to obtain a phase demodulation signal of the sensing optical fiber under each pulse.

[0060] As an example, the preset spatial differential distance is 3, the phase signal queue is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10...., and the two sampling points in each phase signal that are separated by the spatial differential distance are subtracted according to the preset spatial differential distance. The operations performed are 4-1, 5-2, 6-3, 7-4, 8-5, 9-6, 10-7.... The resulting new signal queue is the phase demodulated signal.

[0061] As an example, Figure 4 The phase signal in the sensor fiber is spatially differentially processed to obtain the phase demodulation signal of the sensor fiber at each pulse. Figure 5 shown.

[0062] S5, according to the preset optical fiber sampling position, extract the sampling point corresponding to the optical fiber sampling position in each phase demodulation signal, arrange all the sampling points according to the sampling time, and obtain the vibration signal of the optical fiber sampling position; Figure 6 As shown, the vibration signal is sequentially subjected to windowing processing and FFT transformation, and then the vibration signal is subjected to low-frequency frequency domain compensation according to a preset frequency domain compensation coefficient. After that, the vibration signal after frequency domain compensation is sequentially subjected to IFFT transformation and windowing processing, and the result is output.

[0063] Among them, for short-time Fourier transform, a narrow window has high time resolution and low frequency resolution; a wide window has low time resolution and high frequency resolution; the windowing length of the short-time Fourier transform is determined according to the range of the low-frequency signal that needs to be compensated.

[0064] Optionally, a sine window, a rectangular window, a Hanning window or a Hamming window is used to perform windowing processing on the vibration signal.

[0065] In summary, the first key point of the optical fiber DAS phase demodulation method provided by the embodiment of the present invention is that the cumulative error can be eliminated by taking two adjacent pulse detection signals (the detection signal can be in a polarization state or a non-polarization state) as a reference to perform rotating vector summation, and a frequency domain filter is introduced by using short-time Fourier transform after the rotating vector summation to restore the suppressed low-frequency signal, thereby realizing wide-bandwidth real-time detection of extremely low-frequency to high-frequency signals, and improving the accuracy and stability of signal processing. The second key point is that the optical fiber DAS phase demodulation method provided by the embodiment of the present invention mostly only involves multiplication and addition operations, and the multiplication operations can mostly be calculated in a shifting manner, and the computing resources are very small, which is suitable for deployment on the field programmable gate array FPGA and ZYNQ platform to realize phase demodulation of a completely lower machine, which can greatly reduce the system cost.

[0066] Among them, when the optical fiber DAS phase demodulation method provided by the embodiment of the present invention is deployed on the ZYNQ platform, high-precision demodulation of the complete lower machine can be achieved through the PS end and PL end of ZYNQ.

[0067] An embodiment of the present invention further provides a fiber DAS phase demodulation device, comprising a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program stored in the memory, the steps of the fiber DAS phase demodulation method described above are implemented.

[0068] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0069] The present invention is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems) and computer program products according to the embodiments of the present invention. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions.

[0070] It should be noted that in the claims, any reference numerals placed between brackets shall not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention may be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In the claims enumerating several means, several of these means may be embodied by the same hardware. The use of the words first, second, third, etc., is for convenience of expression only and does not indicate any order. These words may be understood as part of the component name.

[0071] In addition, it should be noted that, in the description of this specification, the description of the terms "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0072] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments after knowing the basic creative concept. Therefore, the claims should be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0073] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention should also include these modifications and variations.

Claims

1. A fiber DAS phase demodulation method, characterized in that: The following steps are involved: S1, collecting digital signals of the sensing optical fiber under each pulse signal emitted by the DAS system; S2, extracting sub-bands and matching filters on the digital signal under each pulse signal and the digital signal under the pulse signal at a preset interval, and then performing adjacent differential rotation vector summation processing to obtain a complex signal; wherein the preset interval is an integer multiple of the pulse signal transmission interval; S3, performing arctan operation on each complex signal to solve the phase angle, and performing phase angle expansion to obtain the phase signal of the sensing optical fiber under each pulse; S4, performing spatial differential processing on each phase signal to obtain a phase demodulation signal of the sensing optical fiber under each pulse; S5. According to the preset optical fiber sampling position, extract the sampling points corresponding to the optical fiber sampling position in each phase demodulation signal, arrange all the sampling points according to the sampling time, and obtain the vibration signal of the optical fiber sampling position; perform windowing and FFT transformation on the vibration signal in turn, and then perform low-frequency frequency domain compensation on the vibration signal according to the preset frequency domain compensation coefficient, and then perform IFFT transformation and windowing on the vibration signal after frequency domain compensation in turn, and output the result.

2. The optical fiber DAS phase demodulation method according to claim 1, characterized in that: The pulse signal transmitted by the DAS system is a single-frequency signal or a swept-frequency signal.

3. The optical fiber DAS phase demodulation method according to claim 1, characterized in that: S2 includes: using the intra-pulse frequency division method to divide the digital signal under each pulse into a preset number of signals of different frequency bands, performing first-order differential processing on the different frequency band signals under each pulse signal and the corresponding frequency band signals of the pulse signal at a preset interval to obtain the first-order differential result corresponding to each pulse signal, adding all the first-order differential results corresponding to each pulse signal to obtain the complex signal of the sensing optical fiber under each pulse.

4. The optical fiber DAS phase demodulation method according to claim 3, characterized in that: In S1, two paths of backward Rayleigh scattered light signals of the sensing optical fiber under each pulse signal emitted by the DAS system are collected, and the two paths of backward Rayleigh scattered light signals are converted into two paths of digital signals.

5. The optical fiber DAS phase demodulation method according to claim 4, characterized in that: The digital signal under each pulse is divided into a preset number of signals with different frequency bands using the intra-pulse frequency division method, including: The two digital signals collected by the sensing optical fiber under each pulse signal emitted by the DAS system are X-channel digital signal DATA_X_M and Y-channel digital signal DATA_Y_M; Copy DATA_X_M to obtain DATA_X_S; copy DATA_Y_M to obtain DATA_Y_S; Input DATA_X_M, DATA_X_S, DATA_Y_M, and DATA_Y_S into their respective corresponding frequency band division links to obtain different frequency band signals corresponding to DATA_X_M, different frequency band signals corresponding to DATA_X_S, different frequency band signals corresponding to DATA_Y_M, and different frequency band signals corresponding to DATA_Y_S; Add the corresponding frequency band signals in DATA_X_M and DATA_X_S, add the corresponding frequency band signals in DATA_Y_M and DATA_Y_S, and output different frequency band signals of the digital signal under each pulse; Among them, the frequency band division link includes at least two sub-band links set in parallel, and the frequency domain coefficients of at least two sub-band links are different from each other; the signal is input into the sub-band link, the signal is sequentially subjected to windowing processing and FFT transformation, and then the signal is subjected to frequency band extraction according to the pre-set sub-band frequency domain coefficients, and then the signal after frequency band extraction is sequentially subjected to IFFT transformation and windowing processing, and the result is output.

6. The optical fiber DAS phase demodulation method according to claim 3, characterized in that: The preset interval is the pulse signal transmission interval.

7. The optical fiber DAS phase demodulation method according to claim 6, characterized in that: Performing first-order difference processing on the different frequency band signals under each pulse signal and the corresponding frequency band signals of the pulse signal at a preset interval therefrom to obtain the first-order difference result corresponding to each pulse signal, including: Different frequency band signals under the pulse signal are alternately stored in the first first-in-first-out memory and the second first-in-first-out memory according to the transmission order of the pulse signal; The different frequency band signals under the current pulse signal are conjugated and sent to the first FIFO memory and the complex multiplier. At the same time, the different frequency band signals under the previous pulse signal are read from the second FIFO memory and sent to the complex multiplier. The corresponding frequency band signals in the two pulse signals are multiplied and output in the complex multiplier to obtain the first-order difference result corresponding to the current pulse signal; or, The different frequency band signals under the current pulse signal are conjugated and sent to the second first-in-first-out memory and the complex multiplier. At the same time, the different frequency band signals under the previous pulse signal are read from the first first-in-first-out memory and sent to the complex multiplier. In the complex multiplier, the corresponding frequency band signals in the two pulse signals are multiplied and output to obtain the first-order difference result corresponding to the current pulse signal.

8. The optical fiber DAS phase demodulation method according to claim 1, characterized in that: In S4, according to the preset spatial differential distance, two sampling points separated by the spatial differential distance in each phase signal are subtracted to obtain a phase demodulation signal of the sensing optical fiber under each pulse.

9. The optical fiber DAS phase demodulation method according to claim 1, characterized in that: In S5, a sine window, a rectangular window, a Hanning window or a Hamming window is used to perform windowing processing on the vibration signal.

10. An optical fiber DAS phase demodulation device, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program stored in the memory, the steps of the optical fiber DAS phase demodulation method according to any one of claims 1 to 9 are implemented.

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