Signal processing device, signal processing method and program

Abstract

Provided is a signal processing device that restores phase difference data of backscattered light of laser light of a discretionary short gauge length from a phase difference signal of the backscattered light of laser light of a long predetermined gauge length. Provided is a signal processing device (1) comprising: an acquisition unit (107) that acquires a phase difference signal of backscattered light of a laser light using an optical fiber sensor that converts dynamic distortion in optical fiber of a first gauge length, which is a predetermined segment, into a phase difference of backscattered light passing through the first gauge length; and a control unit (108) that carries out signal processing so as to obtain, from the acquired phase difference signal of the backscattered light of the laser light, phase difference data of backscattered light of the laser light in a second gauge length, which is shorter than the first gauge length.

Description

[Technical Field]

[0001] The present disclosure relates to a signal processing device, a signal processing method, and program Regarding. [Background technology]

[0002] A method for detecting acoustic signals using optical fiber as a sensor medium has been developed. Patent Document 1 discloses the measurement of vibrations transmitted through optical fiber using optical time domain reflectometry (OTDR). When pulsed light is incident on an optical fiber as a probe light, backscattered light is generated as the pulsed light propagates. The OTDR measures the backscattered light generated at each position along the optical fiber. Vibrations are measured by observing changes in the phase of the backscattered light obtained by the OTDR. Such optical fiber sensors are called distributed acoustic sensors (DAS).

[0003] As shown in Figure 9, when vibration is applied to an optical fiber, the optical fiber in that section is distorted. As a result, the phase difference between the phase of the backscattered light at the beginning of a certain section (the section to be evaluated for phase difference) and the phase of the backscattered light at the end changes by the amount of the fiber distortion. In a non-vibration state, the phase difference of the backscattered light is

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[0004] When the gauge length is small, as shown in the left diagram of Figure 10, the interval over which the phase difference from the reference point to the observation point is evaluated is short, resulting in high spatial resolution, but the signal-to-noise ratio (SN ratio) is small. On the other hand, when the gauge length is large, as shown in the right diagram of Figure 10, the interval over which the phase difference from the reference point to the observation point is evaluated is long, resulting in low spatial resolution, but a high SN ratio. Due to the trade-off between SN ratio and spatial resolution, it is necessary to set the gauge length appropriately depending on the event to be detected (e.g., abnormal sound, earthquake, etc.) and the detection method (e.g., event direction and position estimation, etc.). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 194856 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, an object of the present disclosure is to provide a signal processing device that restores phase difference data of backscattered light of laser light with an arbitrary small gauge length from a phase difference signal of backscattered light of laser light with a large, predetermined gauge length. [Means for solving the problem]

[0007] The signal processing device according to the present disclosure comprises: an acquisition unit that acquires a phase difference signal of the backscattered light of the laser light by an optical fiber sensor that converts a dynamic strain of the optical fiber in a first gauge length, which is a predetermined section, into a phase difference of the backscattered light of the laser light that passes through the first gauge length; and a control unit that processes the signal to obtain phase difference data of the backscattered light of the laser light at a second gauge length that is shorter than the first gauge length from the acquired phase difference signal of the backscattered light of the laser light.

[0008] The signal processing method according to the present disclosure includes: acquiring a phase difference signal of backscattered light of the laser light by an optical fiber sensor that converts dynamic strain of the optical fiber in a first gauge length, which is a predetermined section, into a phase difference of backscattered light of the laser light passing through the first gauge length; and obtaining phase difference data of the backscattered light of the laser light at a second gauge length shorter than the first gauge length from the phase difference signal of the backscattered light of the laser light obtained.

[0009] According to the present disclosure program teeth, acquiring a phase difference signal of backscattered light of the laser light by an optical fiber sensor that converts dynamic strain of the optical fiber in a first gauge length, which is a predetermined section, into a phase difference of backscattered light of the laser light passing through the first gauge length; and obtaining, from the obtained phase difference signal of the backscattered light of the laser light, phase difference data of the backscattered light of the laser light at a second gauge length shorter than the first gauge length. In be. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a signal processing device that restores phase difference data of backscattered light of laser light with an arbitrary small gauge length from a phase difference signal of backscattered light of laser light with a large, predetermined gauge length. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram of an optical fiber sensor according to an embodiment; [Figure 2]10A and 10B are diagrams illustrating spatial difference processing and dummy signal processing according to an embodiment; [Figure 3] 10 is a block diagram of a signal processing device that restores phase difference data of backscattered light of small gauge length laser light from a phase difference signal of backscattered light of large gauge length laser light according to an embodiment. FIG. [Figure 4] FIG. 10 is a flowchart illustrating processing by a spatial difference data calculation unit according to the embodiment. [Figure 5] 10A and 10B are diagrams illustrating the application of spatial differential processing to a phase difference signal of backscattered light of a large gauge length laser beam according to an embodiment. [Figure 6] FIG. 10 is a flowchart illustrating processing performed by a dummy signal removal unit according to the embodiment. [Figure 7] FIG. 10 is a diagram illustrating application of a spatial filter to spatial difference data according to an embodiment. [Figure 8] 10A and 10B are diagrams showing a signal obtained by applying a signal processing device to a signal according to an embodiment and a comparative example; [Figure 9] FIG. 1 illustrates the principle of the associated DAS. [Figure 10] FIG. 1 illustrates the trade-off between signal-to-noise ratio and spatial resolution in an associated DAS. [Figure 11] 1 is a block diagram of a signal processing device according to an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiment Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the invention according to the claims is not limited to the following embodiments. Furthermore, not all of the configurations described in the embodiments are necessarily essential means for solving the problems. For clarity of explanation, the following description and drawings have been omitted and simplified as appropriate. In each drawing, the same elements are given the same reference numerals, and duplicate explanations are omitted as necessary.

[0013] (Optical fiber sensor according to an embodiment) 1 is a block diagram of an optical fiber sensor according to an embodiment of the present invention, and an optical fiber sensor 100 according to the present embodiment will be described with reference to FIG.

[0014] The optical fiber sensor 100 includes an optical fiber 101 , a light source 102 , an optical coupler 103 , an optical modulator 104 , a circulator 105 , a photodetector 106 , an acquisition unit 107 , a control unit 108 , and an output unit 109 .

[0015] The optical fiber 101 is a linear cable that detects backscattered light (Rayleigh scattered light) of the emitted laser light. The optical fiber 101 transmits light. The optical fiber is made of a material capable of transmitting light, such as fibrous quartz glass or plastic, and has a two-layer structure consisting of a central core and a cladding that surrounds the core. One end of the optical fiber is connected to the circulator 105. The optical fiber is connected and disposed at a location where vibration detection is desired.

[0016] The light source 102 is a laser light source with high coherence and narrow linewidth. The laser light source may be a solid-state laser such as a ruby ​​laser or a YAG laser, a liquid laser such as a dye laser, a gas laser such as an excimer laser or a CO2 laser, or a semiconductor laser. The light source 102 emits pulsed light at a constant frequency toward the optical coupler 103 under the control of the control unit 108.

[0017] The optical coupler 103 is a device that splits the pulsed light output from the light source 102 into two. One of the pulsed lights split by the optical coupler 103 is directed to an optical modulator 104, and the other is directed to a photodetector 106.

[0018] The optical modulator 104 is a device that modulates the pulsed light output from the light source 102. The optical modulator can change the wavelength, frequency, intensity, phase, etc. of the light under the control of the control unit 108. The pulsed light modulated by the optical modulator 104 is output to the circulator 105.

[0019] The circulator 105 is a device that outputs the pulsed light output from the optical modulator 104 toward the optical fiber 101. The circulator 105 also outputs the backscattered light that has returned from the optical fiber toward the photodetector .

[0020] The photodetector 106 is a device that measures backscattered light using a coherent detection method. The photodetector 106 receives the pulsed light from the optical coupler 103 and the backscattered light from the circulator 105. Because the backscattered light has a frequency shift due to the modulation of the pulsed light by the optical modulator 104, light of different frequencies is simultaneously input to the photodetector 106. The photodetector 106 measures a beat frequency resulting from the interference of these two optical signals with different frequencies. The beat frequency measured by the photodetector 106 is output to an analog-to-digital converter of the acquisition unit 107 as analog data of the backscattered light. In this way, the phase difference of the backscattered light is detected. The timing of reception of the backscattered light by the photodetector 106 is synchronized with the timing of the pulsed light output from the light source 102 under the control of the control unit 108.

[0021] The acquisition unit 107 acquires a phase difference signal of the backscattered light of the laser light using an optical fiber sensor that converts the dynamic strain of the optical fiber in a first gauge length, which is a predetermined section, into a phase difference of the backscattered light of the laser light passing through the first gauge length. The acquisition unit 107 is a device configured with a semiconductor integrated circuit, etc. The acquisition unit 107, together with the control unit 108, processes analog data related to the backscattered light output from the photodetector 106. The acquisition unit 107 includes an analog-to-digital converter. The analog-to-digital converter is a device that converts the analog data output from the photodetector 106 into digital data. The acquisition unit 107 processes the digital data using a known method, which will not be described in detail here.

[0022] The control unit 108 is a device configured with a semiconductor integrated circuit, just like the acquisition unit 107. The control unit 108 is a central processing unit capable of executing programs. Here, the control unit 108 controls and processes the digital data of the acquisition unit 107. The control unit 108 includes a spatial difference data calculation unit 2 and a dummy signal removal unit 3.

[0023] The output unit 109 is a device such as a display device and a speaker, and outputs data as a display, a sound, or the like.

[0024] (Gauge length manipulation by signal processing) It will be explained that a signal with a different gauge length can be obtained by taking spatial difference data. TIFF0007810256000007.tif11168, the second small gauge length g is shifted in the longitudinal direction of the optical fiber. The spatial difference data at the same time of TIFF0007810256000008.tif11168 is

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[0025] FIG. 2 is a diagram showing spatial difference processing and dummy signal processing according to an embodiment. The explanation of gauge length manipulation by signal processing will be explained with reference to FIG. 2. As shown in the upper diagram of FIG. 2, a phase difference signal of a first gauge length G from point x0 to point x0+G is As shown in the middle of Figure 2, the phase difference data for the second gauge length g is obtained by taking the spatial difference. TIFF0007810256000016.tif11168 and dummy signal As shown in the lower part of Figure 2, the spatial difference data is processed with dummy signals to remove the dummy signals. I get TIFF0007810256000018.tif11168.

[0026] (Signal processing device according to an embodiment) 3 is a block diagram of a signal processing device that restores phase difference data of backscattered light of small gauge length laser light from a phase difference signal of backscattered light of large gauge length laser light according to an embodiment. The signal processing device of this embodiment will be described with reference to FIG.

[0027] The signal processing device 1 of this embodiment restores phase difference data of the backscattered light of the laser light of the second gauge length from the phase difference signal of the backscattered light of the laser light of the first gauge length. As shown in FIG. 3, the signal processing device 1 of this embodiment includes an acquisition unit 107 and a control unit 108. The control unit 108 further includes a spatial difference data calculation unit 2 and a dummy signal removal unit 3. The spatial difference data indicates the spatial difference of the phase difference signal at a position shifted by the second gauge length g in the longitudinal direction of the optical fiber. The spatial difference data calculation unit 2 calculates the phase difference signal of the first gauge length. TIFF0007810256000019.tif11168 is input, and the second gauge length g is set. Then, the spatial difference data calculation unit 2 calculates the phase difference data of the second gauge length as TIFF0007810256000020.tif11168, a dummy signal Restore in a format containing TIFF0007810256000021.tif11168.

[0028] The dummy signal removal unit 3 extracts and removes dummy signals from the spatial difference data by signal processing. The output signal is the phase difference data of the second gauge length. The file is TIFF0007810256000022.tif11168.

[0029] (Input signal according to the embodiment) The phase difference signal of the backscattered light of the laser light of the first gauge length, which is the input signal of this embodiment. Explains TIFF0007810256000023.tif11168. Input signal TIFF0007810256000024.tif11168 is a phase difference signal (proportional to the strain of the optical fiber) or a time-varying phase difference signal (proportional to the strain rate) of backscattered light (Rayleigh scattered light) relative to the incident pulse light, measured by the DAS. Here, if d is the distance of the optical fiber from the optical fiber sensor to the measurement point, then

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[0030] (Spatial difference data calculation unit of the embodiment) Fig. 4 is a flowchart showing processing by a spatial difference data calculation unit according to an embodiment. Fig. 5 is a diagram showing application of spatial difference processing to a phase difference signal of backscattered light of a large gauge length laser beam according to an embodiment. The processing of the spatial difference data calculation unit according to this embodiment will be described with reference to Figs. 4 and 5.

[0031] As shown in Fig. 4, first, a phase difference evaluation target section is determined (S101). The phase difference evaluation target section is a space / time section to be evaluated in the measurement data, and p and q are determined from p0≦p≦p1, q0≦q≦q1. For example, it may be data for 0.1 seconds from a point 1 km to a point 2 km from the sensor. There may also be multiple phase difference evaluation target sections; for example, 10 seconds of data may be divided into 0.1-second intervals, and all of these may be used as individual phase difference evaluation target sections.

[0032] Next, the spatial difference data of the phase difference evaluation target section is calculated (S102). TIFF0007810256000027.tif11168 is the phase difference signal of the backscattered light of the laser light of the first gauge length, If TIFF0007810256000028.tif11168 is the phase difference data of the backscattered light of the laser light of the second gauge length,

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[0033] The above process can be explained with an image. As shown in the left diagram of Figure 5, TIFF0007810256000032.tif11168 is expressed as the signal from the signal source position Pv in the phase difference evaluation section to Pv+N corresponding to the first large gauge length G. When spatial difference processing is performed, F(p, q) is expressed as the signal from the signal source position Pv to Pv+n corresponding to the second small gauge length g, and the signals at the positions Pv-N and Pv+N, as shown in the right diagram of Figure 5.

[0034] (Dummy signal removal unit of the embodiment) Fig. 6 is a flowchart showing processing by a dummy signal removal unit according to an embodiment. Fig. 7 is a diagram showing application of a spatial filter to spatial difference data according to an embodiment. The processing by the dummy signal removal unit according to this embodiment will be described with reference to Figs. 6 and 7.

[0035] As shown in Fig. 6, first, the position of the signal source in the section to be evaluated for phase difference is identified (S201). The position of the signal source refers to the length of the optical fiber distributed from the DAS to the signal when the DAS detects a signal originating from a certain signal source (for example, vibration on the optical fiber).

[0036] To find the position of a signal source within the phase difference evaluation section for one signal source,

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[0037] As shown in Fig. 6, next, spatial filtering is performed on the dummy signal (S202). The spatial filtering on the dummy signal is performed, for example, when p=P max Processing can be performed by setting a window function g(p) with a width N centered on p and multiplying it by the spatial difference data F(p,q). The window function can be, for example, a rectangular window, a Gaussian window, or a Hanning window.

[0038] The Hanning window, which is a window function g(p) used to filter a single signal source, is given as follows:

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[0039] The above processing is explained with an image. As shown in the right diagram of Figure 7, a spatial filter of Nd0 is applied to the signal source position Pv of the spatial difference data F(p,q). As shown in the left diagram of Figure 7, the dummy signal disappears and the desired signal, the phase difference data of the backscattered light of the laser light of the second gauge length, is obtained. The resulting file is TIFF0007810256000041.tif11168.

[0040] Furthermore, part or all of the processing in the signal processing device 1 described above can be realized as a computer program. Such a program can be stored using various types of non-transitory computer-readable media and supplied to a computer. Non-transitory computer-readable media include various types of tangible recording media. Examples of non-transitory computer-readable media include magnetic recording media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / Ws, and semiconductor memories (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, and RAMs (Random Access Memory)). The program may also be supplied to a computer by various types of temporary computer-readable media. Examples of temporary computer-readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable media can supply the program to a computer via wired communication paths such as electric wires and optical fibers, or via wireless communication paths.

[0041] The present disclosure provides a signal processing device that restores phase difference data of backscattered light of laser light of an arbitrary small gauge length from a phase difference signal of backscattered light of laser light of a large, predetermined gauge length. The present disclosure also provides a signal processing method that restores phase difference data of backscattered light of laser light of an arbitrary small gauge length from a phase difference signal of backscattered light of laser light of a large, predetermined gauge length. The present disclosure also provides a readable medium that stores a program for performing a process of restoring phase difference data of backscattered light of laser light of an arbitrary small gauge length from a phase difference signal of backscattered light of laser light of a large, predetermined gauge length. [Example]

[0042] This example shows an application of the signal processing device 1 of this embodiment to a system for detecting contact with an optical fiber. Contact occurred five times in five seconds at a point 261 m to 262 m away from the DAS. The sampling frequency of the analog-to-digital converter was 125 MHz. Using the signal processing device 1 of this embodiment, data with a gauge length of 24 m was restored to data with a gauge length of 0.8 m.

[0043] The phase difference evaluation target interval was set to 220 m≦d≦300 m in space and 0 sec≦t≦5 sec in time. The Hanning window function was used.

[0044] 8 shows a signal obtained by applying a signal processing device to a signal according to the embodiment and a comparative example. The leftmost diagram in Fig. 8 shows a comparative example, which is an input signal with a gauge length of 0.8 m.

[0045] The second figure from the left in Figure 8 shows the phase difference signal of the backscattered light of the laser beam, which is the input signal for a gauge length of 24 m. As can be seen, five contact signals were observed. This phase difference signal also has a high signal-to-noise ratio. However, a signal is generated for a considerable period between 220 m and 300 m, indicating poor spatial resolution.

[0046] The second diagram from the right in Figure 8 shows the phase difference signal after spatial differential processing. From this diagram, we can see that the spatial differential data F(p,q) after spatial differential processing has dummy signals on both sides of the phase difference data of the backscattered light of the laser beam.

[0047] The rightmost image in Figure 8 shows the data after applying a spatial filter to the spatial difference data. Comparing the rightmost image in Figure 8 after applying the filter with the leftmost image, which is a comparative example, reveals that almost identical data was obtained.

[0048] In this way, the signal processing device of this embodiment can restore the phase difference data of the backscattered light of laser light with an arbitrary small gauge length from the phase difference signal of the backscattered light of laser light with a predetermined large gauge length.

[0049] 11 is a block diagram of a signal processing device according to an embodiment of the present invention, which will be described with reference to FIG. The signal processing device 1 according to the embodiment includes an acquisition unit 107 that acquires a phase difference signal of the backscattered light of the laser light using an optical fiber sensor that converts dynamic strain of the optical fiber in a first gauge length, which is a predetermined section, into a phase difference of the backscattered light of the laser light that passes through the first gauge length. The signal processing device 1 according to the embodiment also includes a control unit 108 that acquires phase difference data of the backscattered light of the laser light in a second gauge length that is shorter than the first gauge length from the acquired phase difference signal of the backscattered light of the laser light.

[0050] The signal processing device of this embodiment can restore phase difference data of backscattered light of laser light with an arbitrary small gauge length from a phase difference signal of backscattered light of laser light with a predetermined large gauge length.

[0051] Although the embodiments of the present invention have been described above, the present invention includes appropriate modifications that do not impair the objects and advantages thereof, and is not limited to the above-described embodiments.

[0052] A part or all of the above-described embodiments can be described as, but not limited to, the following supplementary notes. (Appendix 1) an acquisition unit that acquires a phase difference signal of the backscattered light of the laser light by an optical fiber sensor that converts a dynamic strain of the optical fiber in a first gauge length, which is a predetermined section, into a phase difference of the backscattered light of the laser light that passes through the first gauge length; and a control unit that performs signal processing to obtain phase difference data of the backscattered light of the laser light at a second gauge length that is shorter than the first gauge length from the acquired phase difference signal of the backscattered light of the laser light. (Appendix 2) the control unit includes a spatial difference data calculation unit that calculates spatial difference data indicating a spatial difference of a phase difference signal at a position shifted in a longitudinal direction of the optical fiber; 2. The signal processing device according to claim 1, further comprising: a dummy signal removal unit that removes a dummy signal from the spatial difference data. (Appendix 3) the spatial difference data calculation unit obtains spatial difference data of the phase difference signal at a position shifted by the first gauge length, 3. The signal processing device according to claim 2, wherein the dummy signal removal unit identifies a position of a signal source in the predetermined section and filters out the dummy signal. (Appendix 4) To determine the first gauge length, Let d be the distance of the optical fiber from the optical fiber sensor to the measurement point;

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[0053] 1. Signal Processing Device 2. Spatial difference data calculation section 3 Dummy signal removal section 100 Optical fiber sensor 101 Optical Fiber 102 Light source 103 Optical Coupler 104 Optical Modulator 105 Circulator 106 Photodetector 107 Acquisition Department 108 Control Unit 109 Output section

Claims

1. an acquisition unit that acquires a phase difference signal of the backscattered light of the laser light by an optical fiber sensor that converts a dynamic strain of the optical fiber in a first gauge length that is a predetermined section into a phase difference of the backscattered light of the laser light that passes through the first gauge length; a control unit that performs signal processing to obtain phase difference data of the backscattered light of the laser light at a second gauge length that is shorter than the first gauge length, from the acquired phase difference signal of the backscattered light of the laser light, the control unit includes a spatial difference data calculation unit that calculates spatial difference data indicating a spatial difference of a phase difference signal at a position shifted in a longitudinal direction of the optical fiber; a dummy signal removal unit that removes a dummy signal from the spatial difference data, the spatial difference data calculation unit obtains spatial difference data of the phase difference signal at a position shifted by the first gauge length, The dummy signal removal unit identifies the position of a signal source in the predetermined section and filters out dummy signals.

2. To determine the first gauge length: Let d be the distance of the optical fiber from the optical fiber sensor to the measurement point; [Equation 47] where p is an integer and f ADC is the sampling frequency of the optical fiber sensor, and c is c=c 0 / n c In c 0 is the speed of light in a vacuum, and n c is the refractive index of the core of the optical fiber, and d is the speed of light in the optical fiber. 0 is the spacing of the discrete points in the spatial direction, Let t be the measurement time, [Number 48] where q is an integer and f Pulse is the frequency at which the laser light pulses are emitted, The first gauge length G is G=Nd 0 and The second gauge length g is g=nd 0 and N is an integer, and n is an integer less than N; p 0 ≦p≦p 1 ,q 0 ≦q≦q 1 Determine p and q from To obtain spatial difference data of the phase difference signal at the position shifted by the first gauge length, 【number】 is a phase difference signal of the backscattered light of the laser light in the first gauge length, 【number】 is the phase difference data of the backscattered light of the laser light at the second gauge length, [Number 49] [Number 50] Then, the spatial difference data F(p,q) is [0.51] Define and find To identify the location of the signal source in the predetermined interval, [Number 52] Define [Number 53] twist, 【number】 P max of [Number 54] More seeking, To filter the dummy signal, Window Function [Number 55] using the phase difference data of the backscattered light of the laser light at the second gauge length [Number 56] The signal processing device according to claim 1 , wherein the signal processing device calculates:

3. acquiring a phase difference signal of backscattered light of the laser light by an optical fiber sensor that converts dynamic strain of the optical fiber in a first gauge length, which is a predetermined section, into a phase difference of backscattered light of the laser light passing through the first gauge length; and obtaining, from the acquired phase difference signal of the backscattered light of the laser light, phase difference data of the backscattered light of the laser light at a second gauge length shorter than the first gauge length, The step of obtaining phase difference data of the backscattered light of the laser light at the second gauge length includes: calculating spatial difference data indicating spatial differences of phase difference signals at positions shifted in the longitudinal direction of the optical fiber; removing dummy signals from the spatial difference data; the step of calculating the spatial difference data includes a step of obtaining spatial difference data of a phase difference signal at a position shifted by the first gauge length, A signal processing method, wherein the step of removing the dummy signal comprises the steps of identifying a position of a signal source in the predetermined section and filtering the dummy signal.

4. To determine the first gauge length: Let d be the distance of the optical fiber from the optical fiber sensor to the measurement point; [Number 57] where p is an integer and f ADC is the sampling frequency of the optical fiber sensor, and c is c=c 0 / n c In c 0 is the speed of light in a vacuum, and n c is the refractive index of the core of the optical fiber, and d is the speed of light in the optical fiber. 0 is the spacing of the discrete points in the spatial direction, Let t be the measurement time, [Number 58] where q is an integer and f Pulse is the frequency at which the laser light pulses are emitted, The first gauge length G is G=Nd 0 and The second gauge length g is g=nd 0 and N is an integer, and n is an integer less than N; p 0 ≦p≦p 1 ,q 0 ≦q≦q 1 Determine p and q from The step of obtaining spatial difference data of the phase difference signal at the position shifted by the first gauge length includes: 【number】 is a phase difference signal of the backscattered light of the laser light in the first gauge length, 【number】 is the phase difference data of the backscattered light of the laser light at the second gauge length, [Number 59] [Number 60] Then, the spatial difference data F(p,q) is [Number 61] Define and find The step of identifying the position of the signal source in the predetermined section includes: [Number 62] Define [Number 63] twist, 【number】 P max of [Number 64] More seeking, The step of filtering the dummy signal includes: Window Function [Number 65] using the phase difference data of the backscattered light of the laser light at the second gauge length [Number 66] The signal processing method according to claim 3, further comprising the step of:

5. acquiring a phase difference signal of backscattered light of the laser light by an optical fiber sensor that converts dynamic strain of the optical fiber in a first gauge length, which is a predetermined section, into a phase difference of backscattered light of the laser light passing through the first gauge length; and obtaining, from the obtained phase difference signal of the backscattered light of the laser light, phase difference data of the backscattered light of the laser light at a second gauge length shorter than the first gauge length, The step of obtaining phase difference data of the backscattered light of the laser light at the second gauge length includes: calculating spatial difference data indicating spatial differences of phase difference signals at positions shifted in the longitudinal direction of the optical fiber; removing dummy signals from the spatial difference data; the step of calculating the spatial difference data includes a step of obtaining spatial difference data of a phase difference signal at a position shifted by the first gauge length, The step of removing the dummy signal comprises a step of identifying a position of a signal source in the predetermined section and filtering out the dummy signal.

6. To determine the first gauge length, Let d be the distance of the optical fiber from the optical fiber sensor to the measurement point; [Number 67] where p is an integer, f ADC is the sampling frequency of the optical fiber sensor, c is the speed of light in the optical fiber, where c=c 0 / nc, where c 0 is the speed of light in a vacuum and nc is the refractive index of the core of the optical fiber, d 0 is the spacing between discrete points in the spatial direction, Let t be the measurement time, [Number 68] Here, q is an integer and f Pulse is the frequency at which the laser light pulses are emitted. the first gauge length G is G=Nd 0 ; The second gauge length g is g=nd 0 ; N is an integer, and n is an integer less than N; p and q are determined from p 0 ≦p≦p 1 , q 0 ≦q≦q 1 ; The step of obtaining spatial difference data of the phase difference signal at the position shifted by the first gauge length includes: 【number】 is a phase difference signal of the backscattered light of the laser light in the first gauge length, 【number】 is the phase difference data of the backscattered light of the laser light at the second gauge length, [Number 69] [Number 70] Then, the spatial difference data F(p,q) is [Number 71] Define and find The step of identifying the position of the signal source in the predetermined section includes: [Number 72] Define [Number 73] twist, 【number】 P max is the maximum value [Number 74] More seeking, The step of filtering the dummy signal includes: Window Function [Number 75] using the phase difference data of the backscattered light of the laser light at the second gauge length [Number 76] The program according to claim 5, wherein the program calculates:

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