Distributed optical fiber vibration detection device and method

Abstract

The invention provides a distributed optical fiber vibration detection device and method, and relates to the technical field of optical fiber vibration sensing. The distributed optical fiber vibration detection device comprises a high-frequency signal detection subsystem and a distributed position detection subsystem; the distributed position detection subsystem comprises a laser, a first 1 * 2 coupler, a modulator, an amplifier, a first isolator, a second 1 * 2 coupler, a circulator, a sensing optical fiber, a first wavelength division multiplexer, an anti-reflection device, a first 2 * 2 coupler, a first detector and an acquisition card; according to the invention, the frequency of a vibration signal is detected through a high-frequency signal detection subsystem, and collected time-domain signals are restored to obtain the frequency and amplitude of the vibration signal by adopting signal processing methods such as fast Fourier transform; the distributed position detection subsystem is used for detecting the position of a vibration signal, signal processing modes such as IQ demodulation and movement difference are adopted, collected time domain signals are restored to obtain the position of the vibration signal, and the influence of the detection distance on the detection frequency of the vibration signal is broken through.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical fiber vibration sensing, in particular to a distributed optical fiber vibration detection device and method. BACKGROUND

[0002] The optical fiber vibration sensing system has the characteristics of intrinsic safety, insulation, strong environmental resistance, etc. By detecting the environmental vibration signal and analyzing the key characteristic value of the vibration signal, the type of the vibration signal can be inversely calculated to a certain extent. Based on these characteristics, the optical fiber vibration sensing system has wide application prospects in the fields of oil and gas exploration, perimeter security intrusion, large equipment structure health and safety state monitoring, smart city, and rail transit condition tracking. The optical fiber vibration sensor can be divided into three types: point type, defense zone type, and distributed type. Compared with the other two types, the distributed optical fiber vibration sensor can detect vibration signals in a long distance and distributed manner, which is beneficial to vibration detection in a wide area and is the most potential vibration sensing system at present. According to the detection principle, the distributed optical fiber vibration sensing can be divided into two types: interference type and scattering type. The interference type distributed optical fiber vibration sensor uses double interferometers for positioning, which has the problem of poor positioning accuracy. The scattering type distributed optical fiber sensor has high positioning accuracy, but the upper limit of the frequency detection is limited by the detection distance.

[0003] In the prior art, patent CN110285878B discloses a high-frequency response distributed optical fiber vibration sensing device and implementation method. The device controls the bending degree of the optical fiber through the connecting rod. When the optical fiber is vibrated, the connecting rod controls the change of the optical fiber loss, the laser information is received by the detector, and the vibration detection information is obtained according to the light attenuation of the laser. Although this device can detect vibration signals, the detection distance is short. Patent CN112532337B discloses a distributed high-precision optical fiber vibration intrusion and online monitoring detector. The detector uses the Mach-Zehnder interference principle combined with multi-path pulse positioning technology, which can detect the distributed positioning accuracy. However, this method cannot improve the upper limit of the detection distance and the detection frequency. Patent CN112539821A discloses a single-end distributed optical fiber vibration sensing system. The system is provided with a feedback interference loop and a loop, which can expand the upper limit of the frequency. However, due to the use of a single-wavelength laser in the feedback interference loop, the detection performance will be obviously affected by the polarization, and the detection distance and the detection frequency will be affected. Therefore, the present application proposes a distributed optical fiber vibration detection device and method to solve the problems in the prior art. SUMMARY

[0004] In view of the above problems, the application provides a distributed optical fiber vibration detection device and method, which breaks the influence of detection distance on the frequency of the detected vibration signal and simultaneously suppresses the influence of polarization on the detection performance.

[0005] To achieve the object of the application, the application realizes the object by the following technical scheme: a distributed optical fiber vibration detection device, comprising a high-frequency signal detection subsystem and a distributed position detection subsystem, wherein the distributed position detection subsystem comprises a laser, a first 1*2 coupler, a modulator, an amplifier, a first isolator, a second 1*2 coupler, a circulator, a sensing optical fiber, a first wavelength division multiplexer, a back reflection device, a first 2*2 coupler, a first detector and an acquisition card, the distributed position detection subsystem is used for detecting the position of a vibration signal, and the time-domain signal acquired is restored to obtain the position of the vibration signal.

[0006] The high-frequency signal detection subsystem comprises a broadband light source, a second wavelength division multiplexer, a second isolator, a second 2*2 coupler, a delay optical fiber, a third 2*2 coupler, a third isolator, a mirror, a second wavelength division multiplexer, a fourth isolator and a second detector, the high-frequency signal detection subsystem is used for detecting the frequency of a vibration signal, and the time-domain signal acquired is restored to obtain the frequency and amplitude of the vibration signal.

[0007] Further improvement lies in that in the high-frequency signal detection subsystem, the output light of the broadband light source is divided into useful light by the second wavelength division multiplexer and enters the second 2*2 coupler, and after being divided into two beams by the second 2*2 coupler, the two beams enter the delay optical fiber, are coupled at the third 2*2 coupler, are again divided into two beams, pass through the third isolator and the fourth isolator, enter the sensing optical fiber through the circulator, are reflected on the mirror, pass through the circulator, enter the fourth isolator through the second wavelength division multiplexer, pass through the third 2*2 coupler and the delay optical fiber again, and form interference at the second 2*2 coupler, the interference light enters the second detector for photoelectric conversion, and the signal is transmitted to the acquisition card, when the sensing optical fiber is affected by external vibration, the fiber core refractive index and length are affected, thereby affecting the phase of the transmission light, after the adjustment of the delay optical fiber, the light emitted by the broadband light source at the same time passes through the transmission light path and experiences different states to form interference on the second 2*2 coupler, and the frequency of the vibration signal is restored according to the detected signal amplitude change.

[0008] Further improvements are as follows: in the distributed position detection subsystem, the laser output light is divided into two beams after passing through the first 1*2 coupler, one of which enters the modulator to form a detection pulse, then passes through the amplifier, the first isolator, the second 1*2 coupler and the circulator, and then enters the sensing optical fiber, the detection pulse generates backscattered light in the sensing optical fiber, and the backscattered light passes through the circulator and the first wavelength division multiplexer and enters the first 2*2 coupler, the other beam of the laser light directly enters the first 2*2 coupler, the two beams of light form interference at the first 2*2 coupler, the interference light is output into two paths by the first 2*2 coupler and enters the first detector, the analog electrical signal output by the first detector is converted into digital signal by the acquisition card, and the signal is transmitted to the upper computer, when the sensing optical fiber vibrates, the phase of the scattered light of the detection pulse changes, when the coherent light is at the first 2*2 coupler, the intensity of the interference signal is affected by the vibration signal, and the position of the vibration signal is obtained by demodulating the coherent signal.

[0009] Further improvements are as follows: the wavelength of the laser is selected to be 1310-1650 nm, the wavelength of the broadband light source is selected to be 1310-1650 nm, the length of the delay optical fiber is selected to be 1 m-20 km, the length of the sensing optical fiber is selected to be 0.1 m-200 km, and the reflectivity of the reflector is selected to be 1%-100%.

[0010] Further improvements are as follows: the coupling ratios of the first 1*2 coupler, the second 1*2 coupler, the first 2*2 coupler, the second 2*2 coupler and the third 2*2 coupler are all selected to be 50:50, and the first 1*2 coupler, the second 1*2 coupler, the first 2*2 coupler, the second 2*2 coupler and the third 2*2 coupler all adopt equal or non-equal light splitting.

[0011] A distributed optical fiber vibration detection method, comprising the following steps:

[0012] S1: the broadband light source outputs light which is transmitted through an optical path to form two beams of light, the two beams of light are coupled, then split again and transmitted to a sensing optical fiber, transmitted again after reflection and form interference light, and the interference light is photoelectrically converted to obtain a time-domain vibration signal and collected;

[0013] S2: after the time-domain vibration signal is filtered, the frequency and amplitude of the vibration signal are obtained by fast Fourier transform;

[0014] S3: the laser output light is split, one beam forms a detection pulse and is transmitted to the sensing optical fiber, the backscattered light generated by the detection pulse forms interference light with the other split beam, the interference light is processed and a time-domain coherent signal is collected;

[0015] S4: a plurality of groups of time-domain coherent signals are continuously collected, and the vibration position is obtained after processing.

[0016] S5: According to the obtained vibration signal frequency, amplitude and vibration position, distributed detection of the vibration signal on the sensing optical fiber is realized.

[0017] Further improvement lies in that in S1, the light output by the broadband light source enters the second 2*2 coupler after passing through the second wavelength division multiplexer, is split after passing through the second 2*2 coupler, and enters the delay optical fiber, is split again after coupling at the third 2*2 coupler, enters the sensing optical fiber through the third isolator, the fourth isolator and the circulator, and the reflected light reflected by the reflecting mirror enters the second detector for photoelectric conversion after passing through the circulator, the second wavelength division multiplexer, the fourth isolator, the third 2*2 coupler and the delay optical fiber in sequence, and interference light is formed at the second 2*2 coupler, and the interference light enters the second detector for photoelectric conversion, and the time-domain vibration signal is obtained by the acquisition card.

[0018] Further improvement lies in that in S2, the time-domain vibration signal is subjected to noise reduction filtering processing, and after the noise interference is removed, the time-domain signal is converted into a frequency-domain signal through fast Fourier transform, so that the frequency and the corresponding amplitude of the vibration signal are obtained.

[0019] Further improvement lies in that in S3, the light output by the laser enters the first 1*2 coupler for splitting, one of the beams enters the modulator to form a detection pulse, the detection pulse enters the sensing optical fiber through the amplifier, the first isolator, the second 1*2 coupler and the circulator, the backscattered light generated by the detection pulse in the sensing optical fiber enters the first 2*2 coupler through the circulator and the second wavelength division multiplexer, the other beam of light directly enters the first 2*2 coupler, and the two beams of light form interference light at the first 2*2 coupler, the interference light is output from the first 2*2 coupler into the first detector, the analog electrical signal output by the first detector is subjected to analog-digital conversion by the acquisition card, a time-domain coherent signal is obtained, and the length of the time-domain coherent signal is converted into the length of the sensing optical fiber according to the pulse time of flight.

[0020] Further improvement lies in that in S4, a plurality of groups of time-domain coherent signals are continuously acquired, the amplitude curve of the signal is obtained after noise reduction filtering and IQ demodulation, the amplitude curve is processed through the moving difference method, and the position of the vibration is determined.

[0021] The beneficial effects of the present application are:

[0022] The present application detects the vibration signal frequency through the high-frequency signal detection subsystem, restores the collected time-domain signal to obtain the vibration signal frequency and amplitude by using the fast Fourier transform and other signal processing methods, detects the vibration signal position through the distributed position detection subsystem, restores the collected time-domain signal to obtain the vibration signal position by using the IQ demodulation and the moving difference and other signal processing methods, and this method breaks through the influence of the detection distance on the detection of the vibration signal frequency, and simultaneously suppresses the influence of polarization on the detection performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the front view of the present invention;

[0024] Figure 2 This is a time domain vibration signal diagram collected in Example 2 of the present invention;

[0025] Figure 3 This is a frequency domain vibration signal diagram collected in Example 2 of the present invention;

[0026] Figure 4 This is a coherent detection signal diagram collected in Example 2 of the present invention;

[0027] Figure 5 This is a schematic diagram of the vibration signal positioning result according to the second embodiment of the present invention;

[0028] Figure 6 This is a schematic diagram of the optical coherent detection principle of the present invention;

[0029] Figure 7 This is a schematic diagram of digital IQ demodulation according to the present invention;

[0030] Figure 8 This is a schematic diagram of the cooperative operation of the subsystems of the present invention.

[0031] Among them: 1. Laser; 2. First 1*2 coupler; 3. Modulator; 4. Amplifier; 5. First isolator; 6. Second 1*2 coupler; 7. Circulator; 8. Sensing fiber; 9. First wavelength division multiplexer; 10. Anti-reflection device; 11. First 2*2 coupler; 12. First detector; 13. Acquisition card; 14. Broadband light source; 15. Second wavelength division multiplexer; 16. Second isolator; 17. Second 2*2 coupler; 18. Delay fiber; 19. Third 2*2 coupler; 20. Third isolator; 21. Reflector; 22. Second wavelength division multiplexer; 23. Fourth isolator; 24. Second detector. DETAILED DESCRIPTION

[0032] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the examples. The examples are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0033] Example 1

[0034] according to Figure 1 、 2The embodiment shown in 1, 2, 3, 4, 5, 6, 7, 8 proposes a distributed optical fiber vibration detection device, which comprises a high-frequency signal detection subsystem and a distributed position detection subsystem, wherein the distributed position detection subsystem comprises a laser 1, a first 1*2 coupler 2, a modulator 3, an amplifier 4, a first isolator 5, a second 1*2 coupler 6, a circulator 7, a sensing optical fiber 8, a first wavelength division multiplexer 9, a reflection elimination device 10, a first 2*2 coupler 11, a first detector 12 and an acquisition card 13.

[0035] The high-frequency signal detection subsystem comprises a broadband light source 14, a second wavelength division multiplexer 15, a second isolator 16, a second 2*2 coupler 17, a delay optical fiber 18, a third 2*2 coupler 19, a third isolator 20, a reflecting mirror 21, a second wavelength division multiplexer 22, a fourth isolator 23 and a second detector 24.

[0036] In the high-frequency signal detection subsystem, the broadband light source 14 outputs light, which, after passing through the second wavelength division multiplexer 15, is divided into useful light into the second 2*2 coupler 17, and is divided into two beams of light after the second 2*2 coupler 17, and then enters the delay optical fiber 18, is coupled at the third 2*2 coupler 19, is again divided into two beams of light after the third isolator 20 and the fourth isolator 23, enters the sensing optical fiber 8 through the circulator 7, is reflected on the reflecting mirror 21, and after the reflected light passes through the circulator 7, enters the fourth isolator 23 through the second wavelength division multiplexer 22, and again passes through the third 2*2 coupler 19 and the delay optical fiber 18, forms interference at the second 2*2 coupler 17, and the interference light enters the second detector 24 for photoelectric conversion, and the signal is transmitted to the acquisition card 13.

[0037] The distributed position detection subsystem, the laser 1 output light passes through the first 1*2 coupler 2 and is divided into two beams, one of which enters the modulator 3 to form a probe pulse, which is then amplified by the amplifier 4, passes through the first isolator 5, and then enters the second 1*2 coupler 6 and enters the circulator 7, and then passes into the sensing optical fiber 8. The probe pulse generates backscattered light in the sensing optical fiber 8, and then passes through the circulator 7 and the first wavelength division multiplexer 9 into the first 2*2 coupler 11. The other beam of light from the laser 1 is directly coupled into the first 2*2 coupler 11 through the first 1*2 coupler 2. The two beams of light interfere at the first 2*2 coupler 11, and the interference light is output into two paths through the first 2*2 coupler 11 and enters the first detector 12. The analog electrical signal output by the first detector 12 is converted into a digital signal by the acquisition card 13, and the signal is transmitted to the host computer. When the sensing optical fiber 8 vibrates, the phase of the probe pulse scattered light changes. When the coherent signal is interfered at the first 2*2 coupler 11, the intensity of the interference signal is affected by the vibration signal. By demodulating the coherent signal, the vibration signal position is obtained.

[0038] The wavelength of the laser 1 is selected to be 1310-1650nm, the wavelength of the broadband light source 14 is selected to be 1310-1650nm, the length of the delay optical fiber 18 is in the range of 1m-20km, the length of the sensing optical fiber 8 is in the range of 0.1m-200km, and the reflectivity of the mirror 21 is in the range of 1%-100%. The coupling ratios of the first 1*2 coupler 2, the second 1*2 coupler 6, the first 2*2 coupler 11, the second 2*2 coupler 17, and the third 2*2 coupler 19 are all selected to be 50:50, and the first 1*2 coupler 2, the second 1*2 coupler 6, the first 2*2 coupler 11, the second 2*2 coupler 17, and the third 2*2 coupler 19 all use equal or unequal light splitting.

[0039] Example two

[0040] According to Figure 1 , 2 , 3, 4, 5, 6, 7, 8, the present embodiment proposes a distributed optical fiber vibration detection method, which is used to detect a 60kHz vibration signal on a sensing optical fiber about 22km long. The method includes the following steps:

[0041] S1: the light output by the broadband light source 14 is transmitted through an optical path to form two beams of light, the two beams of light are coupled, then split again and transmitted to the sensing optical fiber 8, and after reflection, transmitted again to form interference light, and the interference light is photoelectrically converted to obtain a time-domain vibration signal and collected; the light output by the broadband light source 14 enters the second 2*2 coupler 17 through the second wavelength division multiplexer 15, is split by the second 2*2 coupler 17, enters the delay optical fiber 18 respectively, is coupled at the third 2*2 coupler 19 and split again, enters the sensing optical fiber 8 through the third isolator 20, the fourth isolator 23 and the circulator 7, and the reflected light reflected by the reflecting mirror 21 enters the sensing optical fiber 8 through the circulator 7, the second wavelength division multiplexer 22, the fourth isolator 23, the third 2*2 coupler 19, the delay optical fiber 18 in sequence, and forms interference light at the second 2*2 coupler 17, and the interference light enters the second detector 24 to be photoelectrically converted, and the time-domain vibration signal is collected by the collection card 13. The vibration time-domain signal detected by the collection card 13 is as shown in FIG. Figure 2 .

[0042] S2: after the time-domain vibration signal is filtered to reduce noise, the frequency and amplitude of the vibration signal are obtained through fast Fourier transform; after the time-domain vibration signal is filtered to reduce noise, the time-domain signal is converted into a frequency-domain signal through fast Fourier transform after the noise interference is removed, so that the frequency and corresponding amplitude of the vibration signal are obtained. As shown in FIG. Figure 3 , it can be seen from the figure that the frequency of the vibration signal after signal processing is 60 kHz. The frequency is consistent with the vibration signal applied to the sensing optical fiber 8.

[0043] S3: the light output by the laser 1 is split, one beam forms a probe pulse and is transmitted to the sensing optical fiber 8, and the backscattered light generated in the sensing optical fiber 8 forms interference light with the other split light, and the interference light is processed and the time-domain coherent signal is collected; the light output by the laser 1 is split by the first 1*2 coupler 2, one of which enters the modulator 3 to form a probe pulse, is amplified by the amplifier 4, enters the sensing optical fiber 8 through the first isolator 5, the second 1*2 coupler 6 and the circulator 7, the backscattered light generated in the sensing optical fiber 8 by the probe pulse enters the first 2*2 coupler 11 through the circulator 7 and the second wavelength division multiplexer 22, the other split light directly enters the first 2*2 coupler 11, and the two beams of light form interference light at the first 2*2 coupler 11, the interference light is output from the first 2*2 coupler 11 and enters the first detector 12, the analog electrical signal output by the first detector 12 is analog-digital converted by the collection card 13 to obtain a time-domain coherent signal, and the length of the time-domain coherent signal is converted into the length of the sensing optical fiber 8 according to the pulse flight time. After conversion, the vibration time-domain signal detected by the collection card 13 is as shown in FIG. Figure 4 .

[0044] S4: continuously collect multiple sets of time domain coherent signals, and obtain the vibration position after processing; continuously collect multiple sets of time domain coherent signals, and obtain the amplitude curve of the signal after noise reduction filtering and IQ demodulation, process the amplitude curve by moving difference method to determine the position of the vibration. Continuously collect multiple sets of time domain coherent signals as shown in Figure 4 , and the results are shown in Figure 5 . As can be seen from the figure, the vibration signal application position is at 20.3 km, which is about 2 km away from the tail end of the sensing optical fiber 8, which is consistent with the actual vibration signal application position.

[0045] S5: according to the obtained vibration signal frequency, amplitude and vibration position, realizing the distributed detection of the vibration signal on the sensing optical fiber 8.

[0046] It is shown by the embodiment that the application can break through the influence of the upper limit of the vibration signal detection frequency on the detection distance, and realize the detection of wide frequency vibration signals under long detection distance.

[0047] Verification data:

[0048] Distributed position detection subsystem formula principle

[0049] (1) Coherent detection

[0050] Simplify the system, in the coherent detection, see Figure 6 , assume that the light field of the probe light and the reference light are respectively:

[0051]

[0052]

[0053] Signal light and local oscillator light After optical mixing through a 2*2 port 3dB coupler, the light field distribution of the output two ports is respectively and , then the corresponding photoelectric current and can be represented as:

[0054]

[0055]

[0056] In the formula, the photoelectric current of each path is composed of three terms: the first two terms are only related to the amplitudes of the signal light and the local oscillator light, and the third term is related to the frequency and phase of the light field distribution. The photoelectric current of the balanced detector can be represented as:

[0057]

[0058] The photoelectric current of the photoelectric detector responding to the single-channel signal input:

[0059]

[0060] Compared with the common single-channel coherent detection, the two-channel input balanced heterodyne detector can effectively suppress the local light noise and the common-mode signal generation, while the useful signal strength is doubled, and the signal-to-noise ratio of the system is improved.

[0061] (2) IQ demodulation

[0062] The coherent detection method can convert the optical frequency of the sensing signal to a few hundred megahertz of heterodyne intermediate frequency, so that the amplitude and phase information of the sensing signal can be obtained by demodulating the intermediate frequency signal. The digital quadrature demodulation method can convert the intermediate frequency signal into two quadrature components, so that the amplitude information and phase information of the vibration signal can be obtained at the same time, thereby realizing accurate amplitude positioning and quantitative phase restoration of the vibration signal. The digital quadrature demodulation process is shown in Figure 7

[0063] The photoelectric current i(t) is expressed as:

[0064] Firstly, the beat frequency signal passes through a band-pass filter, only the intermediate frequency signal with a frequency component of fAOM is retained, and environmental noise, thermal noise and shot noise are eliminated. The intermediate frequency signal and two quadrature signals with the same frequency and are multiplied respectively to obtain the mixing signals I(t) and Q(t).

[0065]

[0066]

[0067] After the sum-difference product processing, the mixing signals are converted to:

[0068]

[0069]

[0070] Among them, the zero-frequency component retains the phase signal. The mixing signals are respectively processed by low-pass filtering to retain only the zero-frequency component. The filtered mixing signals are expressed as:

[0071]

[0072]

[0073] ​The amplitude information and the phase information of the vibration signal obtained according to the above formula are:

[0074]

[0075]

[0076] wherein k is an integer. Thus, the amplitude information and the phase information of the detection signal are obtained respectively.

[0077] (3) Moving difference

[0078] The signal is filtered by using the sliding average algorithm, so that the amplitude fluctuation of the back Rayleigh scattering light caused by the laser phase noise and the electric noise can be further reduced, and compared with the simple average algorithm, the frequency response range can be increased, and the signal-to-noise ratio can be improved.

[0079] The basic idea of the sliding average algorithm is to sequentially average the data items in the window according to a certain average window size, and continue to average after moving one item each time until only one window size of items is left. wherein ri represents the i-th original scattering light signal. If the sliding average number is M, then the average light signal is , K=N-M+1; and:

[0080]

[0081] From the principle, this algorithm does not reduce the number of original signals by the average number of times, but directly reduces the corresponding number according to the sliding average number.

[0082] Although the average window is set to a larger number, a more smooth curve and a higher signal-to-noise ratio can be obtained, but when a certain threshold is reached, the curve will be deteriorated, and excessive smoothing will lead to the useful information in the curve being filtered out, and the signal-to-noise ratio will be lower than that when the average window is smaller. The bottleneck of the difference sliding average algorithm is that it is difficult to quickly find a suitable filter window to improve the positioning accuracy, so considering a positioning algorithm that combines filtering and difference algorithm to retain as much useful signal as possible while removing noise is a way to improve the signal-to-noise ratio of the difference signal.

[0083] The present application detects the frequency of the vibration signal through a high-frequency signal detection subsystem, restores the time-domain signal collected to obtain the frequency and amplitude of the vibration signal by using a fast Fourier transform and other signal processing methods; detects the position of the vibration signal through a distributed position detection subsystem, restores the time-domain signal collected to obtain the position of the vibration signal by using IQ demodulation, moving difference and other signal processing methods. This method breaks through the influence of the detection distance on the detection of the frequency of the vibration signal, and at the same time suppresses the influence of polarization on the detection performance.

[0084] The foregoing presents and describes the basic principles, main features and advantages of the present application. It should be understood by those skilled in the art that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A distributed optical fiber vibration detection device, comprising a high-frequency signal detection subsystem and a distributed position detection subsystem, characterized in that: The distributed position detection subsystem comprises a laser (1), a first 1*2 coupler (2), a modulator (3), an amplifier (4), a first isolator (5), a second 1*2 coupler (6), a circulator (7), a sensing optical fiber (8), a first wavelength division multiplexer (9), an anti-reflection device (10), a first 2*2 coupler (11), a first detector (12), and an acquisition card (13). The distributed position detection subsystem is used to detect the position of the vibration signal and restore the collected time domain signal to obtain the vibration signal position; The high-frequency signal detection subsystem comprises a broadband light source (14), a second wavelength division multiplexer (15), a second isolator (16), a second 2*2 coupler (17), a time-delay optical fiber (18), a third 2*2 coupler (19), a third isolator (20), a reflector (21), a second wavelength division multiplexer (22), a fourth isolator (23), and a second detector (24). The high-frequency signal detection subsystem is used to detect the frequency of the vibration signal and restore the collected time domain signal to obtain the frequency and amplitude of the vibration signal.

2. A distributed optical fiber vibration detection device according to claim 1, characterized in that: In the high-frequency signal detection subsystem, the output light of the broadband light source (14) passes through the second wavelength division multiplexer (15), and the useful light is separated and enters the second 2*2 coupler (17). After being divided into two beams by the second 2*2 coupler (17), the two beams respectively enter the delay optical fiber (18), are coupled at the third 2*2 coupler (19), and are again divided into two beams. After passing through the third isolator (20) and the fourth isolator (23), the two beams pass through the circulator (7) and enter the sensing optical fiber (8), and are reflected on the reflector (21). After the reflected light passes through the circulator (7), it passes through the second wavelength division multiplexer (22) and enters the fourth isolator (23). After passing through the third 2*2 coupler (19) and the delay optical fiber (18) again, interference is formed at the second 2*2 coupler (17). The interference light enters the second detector (24) for photoelectric conversion, and the signal is transmitted to the acquisition card (13). When the sensing optical fiber (8) is affected by external vibration, the refractive index and length of the optical fiber core are affected, thereby affecting the phase of the transmitted light. After adjustment by the delay optical fiber (18), the light emitted by the broadband light source (14) at the same time will experience different states after passing through the transmission optical path and form interference on the second 2*2 coupler (17). According to the detected signal amplitude change, the frequency of the vibration signal is restored.

3. A distributed optical fiber vibration detection device according to claim 1, characterized in that: In the distributed position detection subsystem, the output light of the laser (1) is divided into two beams after passing through the first 1*2 coupler (2), one of which enters the modulator (3) to form a detection pulse, which is then amplified by the amplifier (4) and passes through the first isolator (5) and then enters the circulator (7) through the second 1*2 coupler (6), and then is transmitted into the sensing optical fiber (8). The detection pulse generates backscattered light in the sensing optical fiber (8), and passes through the circulator (7) and the first wavelength division multiplexer (9) to enter the first 2*2 coupler (11). The other beam of light separated by the laser (1) through the first 1*2 coupler (2) is A beam of light is directly coupled into the first 2*2 coupler (11), and the two beams of light form interference at the first 2*2 coupler (11). The interference light is output into two paths through the first 2*2 coupler (11) and enters the first detector (12). The acquisition card (13) performs analog-to-digital conversion on the analog electrical signal output by the first detector (12) and transmits the signal to the host computer. When the sensing optical fiber (8) vibrates, the phase of the detection pulse scattered light changes. When coherence occurs at the first 2*2 coupler (11), the interference signal intensity is affected by the vibration signal. By demodulating the coherent signal, the vibration signal position is obtained.

4. A distributed optical fiber vibration detection device according to claim 1, characterized in that: The wavelength of the laser (1) is selected to be 1310-1650 nm, the wavelength of the broadband light source (14) is selected to be 1310-1650 nm, the length of the delay optical fiber (18) is in the range of 1 m to 20 km, the length of the sensing optical fiber (8) is in the range of 0.1 m to 200 km, and the reflectivity of the reflector (21) is in the range of 1% to 100%.

5. The distributed optical fiber vibration detection device according to claim 1, characterized in that: The coupling ratios of the first 1*2 coupler (2), the second 1*2 coupler (6), the first 2*2 coupler (11), the second 2*2 coupler (17), and the third 2*2 coupler (19) are all selected to be 50:50, and the first 1*2 coupler (2), the second 1*2 coupler (6), the first 2*2 coupler (11), the second 2*2 coupler (17), and the third 2*2 coupler (19) all adopt equal-ratio optical coupling or non-equal-ratio optical coupling.

6. A distributed optical fiber vibration detection method, using a distributed optical fiber vibration detection device according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: The output light of the broadband light source (14) is transmitted through the optical path to form two beams of light. The two beams of light are coupled and split again and transmitted to the sensing optical fiber (8). After reflection, they are transmitted again to form interference light. The interference light is photoelectrically converted to obtain a time domain vibration signal and collected; S2: After performing noise reduction filtering on the time domain vibration signal, the frequency and amplitude of the vibration signal are obtained through fast Fourier transform; S3: The laser (1) outputs light beams, one beam forms a detection pulse and is transmitted to the sensing fiber (8). The generated backscattered light forms interference light with the other beam, and the interference light is processed and the time domain coherent signal is collected; S4: Continuously collect multiple sets of time domain coherent signals and obtain the vibration position after processing; S5: Based on the obtained vibration signal frequency, amplitude and vibration position, distributed detection of the vibration signal on the sensing optical fiber (8) is achieved.

7. A distributed optical fiber vibration detection method according to claim 6, characterized in that: In the S1, the light output by the broadband light source (14) passes through the second wavelength division multiplexer (15) and enters the second 2*2 coupler (17). After being split by the second 2*2 coupler (17), the light enters the delay optical fiber (18) respectively. After being coupled at the third 2*2 coupler (19), the light is split again. After passing through the third isolator (20), the fourth isolator (23) and the circulator (7), the light enters the sensing optical fiber (8). The reflected light reflected by the reflector (21) passes through the circulator (7), the second wavelength division multiplexer (22), the fourth isolator (23), the third 2*2 coupler (19), and the delay optical fiber (18) in sequence, and forms interference light at the second 2*2 coupler (17). The interference light enters the second detector (24) for photoelectric conversion, and is collected by the acquisition card (13) to obtain a time domain vibration signal.

8. A distributed optical fiber vibration detection method according to claim 7, characterized in that: In S2, the time domain vibration signal is subjected to noise reduction filtering to remove noise interference, and then the time domain signal is converted into a frequency domain signal by fast Fourier transform, thereby obtaining the frequency and corresponding amplitude of the vibration signal.

9. A distributed optical fiber vibration detection method according to claim 6, characterized in that: In the S3, the output light of the laser (1) is split by the first 1*2 coupler (2), one of which enters the modulator (3) to form a detection pulse, is amplified by the amplifier (4), the first isolator (5), the second 1*2 coupler (6), and the circulator (7), and enters the sensing optical fiber (8). The backscattered light generated by the detection pulse in the sensing optical fiber (8) enters the first 2*2 coupler (11) through the circulator (7) and the second wavelength division multiplexer (22). The other split light directly enters the first 2*2 coupler (11). The two light beams form interference light at the first 2*2 coupler (11). The interference light is output through the first 2*2 coupler (11) and enters the first detector (12). The acquisition card (13) performs analog-to-digital conversion on the analog electrical signal output by the first detector (12) to obtain a time-domain coherent signal, and the length of the time-domain coherent signal is converted into the length of the sensing optical fiber (8) according to the pulse flight time.

10. A distributed optical fiber vibration detection method according to claim 9, characterized in that: In the above-mentioned S4, multiple groups of time-domain coherent signals are continuously collected, and the amplitude curve of the signal is obtained after noise reduction filtering and IQ demodulation. The amplitude curve is processed by the moving difference method to determine the position of the vibration.

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