Distributed optical fiber sensing system and method for simultaneous vibration and temperature measurement

Abstract

The present invention provides a distributed optical fiber sensing system and method for realizing simultaneous measurement of vibration and temperature, including a narrow linewidth laser, a tunable laser and a grating array; the detection pulse light obtained by the laser emitted by the narrow linewidth laser and the tunable laser after passing through a laser amplifier is transmitted to an optical circulator 1; the optical circulator 1 is also connected to a grating array and an optical circulator 2; the optical circulator 2 is connected to a strong reflection grating and an unbalanced Mach-Zehnder interferometer; the strong reflection grating and the unbalanced Mach-Zehnder interferometer are both connected to a photodetector. The present invention integrates wavelength demodulation and phase demodulation in the same system, realizes distributed temperature sensing by demodulating the drift of the chirped grating array spectrum, and realizes distributed vibration measurement by measuring the phase change of the interference signal of the reflected pulse of the adjacent chirped grating array. The system can realize accurate measurement of distributed temperature and vibration at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of distributed optical fiber sensing, and in particular to a distributed optical fiber sensing system and method for realizing simultaneous measurement of dual parameters of vibration and temperature. Background Art

[0002] Fiber optic sensing technology is a sensing technology that uses optical fiber as a medium and light as a carrier to sense and transmit external signals. When light is transmitted in an optical fiber, changes in the external environment will cause corresponding changes in various characteristics of the transmitted light. By monitoring the changes in light wave parameters, information about the external environment of the optical fiber can be obtained, thereby realizing sensing. In fiber optic sensing technology, distributed fiber optic sensing technology can continuously and stably measure parameters along the optical fiber over a large range, and plays an irreplaceable role in fiber optic sensing technology. At present, distributed fiber optic sensing technology has been widely used in perimeter security, oil exploration and development, and large-scale structural health monitoring. Distributed fiber optic sensing technology mainly uses scattered signals and optical time domain reflection technology in optical fibers for sensing. Among them, Raman scattered light is more sensitive to temperature changes and is used to realize distributed temperature measurement. Brillouin scattering is more sensitive to temperature and strain changes and is used to realize distributed temperature and strain sensing, while Rayleigh scattering is mostly used for distributed vibration sensing. However, due to the limitations of their own principles and structures, they can only measure single parameters separately. However, in some specific applications, such as oil pipeline leakage monitoring, status monitoring during oil exploration and development, etc., the measurement of a single parameter is far from meeting the needs, and the simultaneous measurement of multiple parameters has gradually become the focus of attention.

[0003] At present, some teams have proposed solutions for simultaneous measurement of multiple parameters in response to the above application requirements. Among them, the MNAlahbabi research group of the University of Southampton proposed a fusion system of Brillouin optical time domain reflectometer (BOTDR) and Raman optical time domain reflectometer (ROTDR), which realized the simultaneous measurement of temperature and strain; the Rao Yunjiang research group of the University of Electronic Science and Technology proposed a fusion system of phase-sensitive optical time domain reflectometer (Φ-OTDR) and polarization optical time domain reflectometer (POTDR), which realized the simultaneous acquisition of polarization and phase information to measure multiple parameters; the Zhang Xuping research group of Nanjing University proposed a fusion system of POTDR and BOTDR, which realized the simultaneous measurement of strain and vibration. The above methods all use scattered light in the optical fiber as the sensing signal. Due to the low scattering coefficient, the intensity of scattered light is often 10-6 to 10-8 of the intensity of the incident light, so the signal-to-noise ratio of the system is relatively low, which greatly limits the sensing distance and spatial resolution. In addition, the temperature and pressure values ​​measured by scattered light are averaged after regional sampling, and the positioning error is large.

[0004] Therefore, how to provide a fiber array distributed fiber optic sensing system and method that can achieve simultaneous high-precision measurement of vibration and temperature is an urgent problem that needs to be solved by those skilled in the art. Summary of the invention

[0005] In view of this, the present invention adopts a sensing grating array, integrates wavelength demodulation and phase demodulation in the same system, realizes distributed temperature sensing by demodulating the drift of the chirped grating array spectrum, and simultaneously measures the phase change of the reflected pulse interference signal of the adjacent chirped grating array to realize distributed vibration measurement. The system can simultaneously realize distributed temperature and vibration measurement, reduce the system cost and meet the needs of multi-parameter measurement in fields such as oil exploration and development.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A distributed optical fiber sensing system for realizing simultaneous measurement of vibration and temperature, comprising a narrow linewidth laser, a tunable laser and a grating array; the detection pulse light obtained by the laser emitted by the narrow linewidth laser and the tunable laser after passing through a laser amplifier is transmitted to an optical circulator 1; the optical circulator 1 is also connected to the grating array and the optical circulator 2; the optical circulator 2 is connected to a strong reflection grating and an unbalanced Mach-Zehnder interferometer; the strong reflection grating and the unbalanced Mach-Zehnder interferometer are both connected to a photodetector;

[0008] The optical circulator 1 is used to input the detection pulse light from the first port and inject it into the grating array from the second port, and the reflected light pulse of the grating array is then output from the third port of the optical circulator 1 to the optical circulator 2;

[0009] The optical circulator 2 is used to input the reflected light pulse output by the optical circulator 1 through the first port, and then output it from the second port of the optical circulator 2 (10) to the strong reflection grating (11), and the reflected pulse of the strong reflection grating (11) is output from the third port to the unbalanced Mach-Zehnder interferometer (13);

[0010] The strong reflection grating is used to reflect the detection pulse light of the narrow line width laser through the detection pulse light of the tunable laser, and the reflected detection pulse light of the narrow line width laser is output to the unbalanced Mach-Zehnder interferometer through the third port of the second optical circulator;

[0011] The unbalanced Mach-Zehnder interferometer is used to generate interference on reflected pulses of adjacent gratings in the grating array, and output the interference light in phase to different photoelectric detectors.

[0012] Preferably, the narrow linewidth laser is used to emit continuous high-coherence laser light; and the tunable laser is used to emit continuous frequency-sweep laser light of different wavelengths in sequence.

[0013] Preferably, the laser amplifier comprises a semiconductor laser amplifier 1, a semiconductor laser amplifier 2, a pulse signal generator and an erbium-doped fiber amplifier;

[0014] The semiconductor laser amplifier 1 is connected to the pulse signal generator and is used to modulate the continuous light output by the narrow linewidth laser into a detection light pulse and output it to the optical fiber coupler;

[0015] The semiconductor laser amplifier 2 is connected to the pulse signal generator and is used to modulate the continuous light output by the tunable laser into a detection light pulse and output it to the optical fiber coupler;

[0016] The optical fiber coupler inputs the coupled detection light pulse into the erbium-doped optical fiber amplifier.

[0017] Preferably, the grating array is a chirped fiber grating array, and adjacent gratings are arranged at a fixed interval.

[0018] Preferably, the strong reflection grating is a narrow-band grating whose central wavelength is consistent with the wavelength of laser light emitted by the narrow-linewidth laser.

[0019] Preferably, one arm of the unbalanced Mach-Zehnder interferometer is provided with a delay optical fiber with a length of 2L, where L is the spacing between adjacent gratings in the grating array; the pulsed light reflected by adjacent chirped fiber gratings generates interference in the unbalanced Mach-Zehnder interferometer, and the interference signal is divided into three signals with a phase difference of ° through a × coupler, and the three signals are input into three photodetectors.

[0020] The present invention also provides a distributed optical fiber sensing method according to the distributed optical fiber sensing system for realizing simultaneous vibration and temperature measurement, comprising the following steps:

[0021] The laser light emitted by the narrow line width laser and the tunable laser is amplified and the obtained detection pulse light is transmitted to the optical circulator 1;

[0022] The optical circulator 1 injects the detection pulse light into the grating array, and the reflected light pulse of the grating array is then output to the optical circulator 2 through the optical circulator 1;

[0023] The optical circulator 2 injects the reflected light pulse output by the optical circulator 1 into the strong reflection grating;

[0024] The strong reflection grating is detected by a tunable laser pulse light and output to a photodetector 1 to obtain reflection signals of the grating array at different wavelengths. The intensity values ​​of the reflection signals at different wavelengths are fitted to restore the reflection spectrum of the grating array. The temperature change around the grating array is detected by the change of the reflection spectrum to realize distributed temperature sensing.

[0025] The strong reflection grating reflects the detection pulse light of the narrow line width laser, and the reflected detection pulse light of the narrow line width laser is output to the unbalanced Mach-Zehnder interferometer through the second optical circulator;

[0026] The unbalanced Mach-Zehnder interferometer generates interference on the reflected pulses of adjacent gratings in the grating array, and outputs the interference light in phase to different photodetectors. The vibration signal around the grating array is restored by demodulating the phase change of the interference signal, thereby realizing distributed vibration sensing.

[0027] It can be seen from the above technical solution that, compared with the prior art, the beneficial effects of the present invention include:

[0028] The wavelength demodulation and interference demodulation technology of the grating are integrated into one system. The external temperature is measured by measuring the change in the grating wavelength. At the same time, the phase change of the reflected pulse interference signal between adjacent gratings is measured to restore the external vibration signal. Since the grating is used to measure the external physical quantity, it is a physical positioning method, so the positioning accuracy is very high. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the provided drawings without creative work.

[0030] Figure 1 A schematic diagram of the structure of a distributed optical fiber sensing system for realizing simultaneous measurement of vibration and temperature provided by an embodiment of the present invention;

[0031] Figure 2 A schematic diagram of the variation of the chirped grating spectrum with temperature measured in an embodiment of the present invention;

[0032] Figure 3 A schematic diagram of an interference pulse sequence between adjacent gratings in a grating array measured by an embodiment of the present invention;

[0033] Figure 4 The time domain spectrum of a 90 Hz sinusoidal signal measured in an embodiment of the present invention;

[0034] Figure 5 This is a frequency domain spectrum of a 90 Hz sinusoidal signal measured in an embodiment of the present invention.

[0035] In the figure, 1 is a narrow linewidth laser, 2 is a tunable laser, 3 is a semiconductor laser amplifier 1, 4 is a semiconductor laser amplifier 2, 5 is a pulse signal generator, 6 is a fiber coupler, 7 is an erbium-doped fiber amplifier, 8 is an optical circulator 1, 9 is a grating array, 10 is an optical circulator 2, 11 is a strong reflection grating, 12 is a photodetector 1, 13 is an unbalanced Mach-Zehnder interferometer, 14 is a photodetector 2, 15 is a photodetector 3, 16 is a photodetector 4, and 17 is a data acquisition card. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The first aspect of the present embodiment discloses a distributed optical fiber sensing system for realizing simultaneous measurement of vibration and temperature, comprising a narrow linewidth laser 1, a tunable laser 2 and a grating array 9; the detection pulse light obtained by the laser emitted by the narrow linewidth laser 1 and the tunable laser 2 after passing through a laser amplifier is transmitted to an optical circulator 1 8; the optical circulator 1 8 is also connected to the grating array 9 and the optical circulator 2 10; the optical circulator 2 10 is connected to a strong reflection grating 11 and an unbalanced Mach-Zehnder interferometer 13; the strong reflection grating 11 and the unbalanced Mach-Zehnder interferometer 13 are both connected to a photodetector;

[0038] An optical circulator 1 8 is used to input the detection pulse light from the first port and inject it into the grating array 9 from the second port, and the reflected light pulse of the grating array 9 is then output from the third port of the optical circulator 1 8 to the optical circulator 2 10;

[0039] The optical circulator 10 is used to input the reflected light pulse output by the optical circulator 1 8 from the first port, and then output it from the second port of the optical circulator 10 to the strong reflection grating 11, and the reflected pulse of the strong reflection grating 11 is output from the third port of the optical circulator 10 to the unbalanced Mach-Zehnder interferometer 13;

[0040] A strong reflection grating 11 is used to reflect the detection pulse light of the narrow line width laser 1 through the detection pulse light of the tunable laser 2, and the reflected detection pulse light of the narrow line width laser 1 is output to the unbalanced Mach-Zehnder interferometer 13 through the third port of the optical circulator 10;

[0041] The unbalanced Mach-Zehnder interferometer 13 is used to generate interference between the reflected pulses of adjacent gratings in the grating array 9 and output the interference light in phase to different photodetectors, such as Figure 1shown.

[0042] In one embodiment: a narrow linewidth laser 1 is used to generate continuous high coherence laser light to a semiconductor laser amplifier 3;

[0043] The tunable laser 2 is used to emit continuously swept lasers of different wavelengths in sequence to the semiconductor laser amplifier 2 4 .

[0044] In one embodiment, the laser amplifier includes a semiconductor laser amplifier 1 3, a semiconductor laser amplifier 2 4, a pulse signal generator 5 and an erbium-doped fiber amplifier 7. The semiconductor laser amplifier 1 3 and the semiconductor laser amplifier 2 4 are used to modulate continuous light into a detection light pulse and output it to the erbium-doped fiber amplifier 7.

[0045] In this embodiment, semiconductor laser amplifier 1 3 is connected to pulse signal generator 5, which is used to modulate the continuous light output by narrow linewidth laser 1 into detection light pulse, and output it to fiber coupler 6; semiconductor laser amplifier 2 4 is connected to pulse signal generator 5, which is used to modulate the continuous light output by tunable laser 2 into detection light pulse, and output it to fiber coupler 6; fiber coupler 6 inputs the coupled detection light pulse to erbium-doped fiber amplifier 7.

[0046] In one embodiment, the grating array 9 is a chirped fiber grating array, and adjacent gratings are arranged at a fixed interval.

[0047] In one embodiment, the erbium-doped fiber amplifier 7 is used to amplify the power of the detection pulse light and output it to the first port of the circulator;

[0048] In one embodiment, an arm of the unbalanced Mach-Zehnder interferometer 13 is provided with a delay optical fiber with a length of 2L, where L is the spacing between adjacent gratings in the grating array; the pulsed light reflected by adjacent chirped fiber gratings generates interference in the unbalanced Mach-Zehnder interferometer 13, and the interference signal is divided into three signals with a phase difference of 120° through a 3×3 coupler, and the three signals are output to the photodetector 2 14, the photodetector 3 15, and the photodetector 4 16 respectively;

[0049] In one embodiment, photodetector 1 12, photodetector 2 14, photodetector 3 15 and photodetector 4 16 are used to convert optical signals into electrical signals and upload them to a data acquisition card.

[0050] In one embodiment, the data acquisition card 17 is used to receive the reflected pulse electrical signal of the tunable laser reflected by the grating array and the electrical signal of the interference light of the grating array, and perform subsequent data processing.

[0051] The second aspect of this embodiment further discloses a distributed optical fiber sensing method for realizing the distributed optical fiber sensing system for simultaneously measuring vibration and temperature based on the first aspect, comprising the following steps:

[0052] The lasers emitted by the narrow line width laser 1 and the tunable laser 2 are amplified and the obtained detection pulse light is transmitted to the optical circulator 8;

[0053] The optical circulator 1 8 injects the detection pulse light into the grating array 9, and the reflected light pulse of the grating array 9 is then output to the optical circulator 2 10 through the optical circulator 1 8;

[0054] The optical circulator 2 10 injects the reflected light pulse output by the optical circulator 1 8 into the grating array, and the reflected light of the grating array 9 is then output to the strong reflection grating 11 through the optical circulator 2 10;

[0055] The strong reflection grating 11 passes through the detection pulse light of the tunable laser 2 and outputs it to the photodetector 12, obtaining the reflection signal of the grating array 9 at different wavelengths, fitting the intensity values ​​of the reflection signals at different wavelengths, restoring the reflection spectrum of the grating array 9, detecting the temperature change around the grating array 9 through the change of the reflection spectrum, and realizing distributed temperature sensing;

[0056] The strong reflection grating 11 reflects the detection pulse light of the narrow line width laser 1, and the reflected detection pulse light of the narrow line width laser 1 is output to the unbalanced Mach-Zehnder interferometer 13 through the optical circulator 10;

[0057] The unbalanced Mach-Zehnder interferometer 13 generates interference with the reflected pulses of adjacent gratings in the grating array 9, and outputs the interference light in phase to different photodetectors. The vibration signal around the grating array 9 is restored by demodulating the phase change of the interference signal, thereby realizing distributed vibration sensing.

[0058] It should be understood that the functions implemented by the above distributed optical fiber sensing method for simultaneous measurement of vibration and temperature correspond one-to-one to the distributed optical fiber sensing system for simultaneous measurement of vibration and temperature provided by the above embodiment, which is a more detailed processing flow implemented by the system.

[0059] The specific implementation steps of the present invention are as follows:

[0060] The narrow linewidth laser 1 emits continuous high coherence light with a wavelength of 1550.1nm and an output power of 10mW. The continuous light reaches the semiconductor laser amplifier 3. The tunable laser 2 sequentially emits continuous light of different wavelengths to the semiconductor laser amplifier 4. The wavelength scanning range is 1551-1555nm, and the wavelength scanning step is 10pm. The pulse signal generator 5 drives the semiconductor laser amplifier 3 and the semiconductor laser amplifier 4 to adjust the continuous light into a detection light pulse with a pulse width of 30ns and a repetition frequency of 10kHz, and outputs it to the erbium-doped fiber amplifier 7. After the pulse light is amplified, it enters the chirped fiber grating array 9 through the optical circulator 8, and the spacing between adjacent gratings is 5m. Each grating will reflect back a part of the pulse light, and the reflected light will reach a narrowband grating with a central wavelength of 1550.1nm after passing through the optical circulator 10. Its 3dB bandwidth is 0.1nm and the reflectivity exceeds 99%. The light of the narrow linewidth light source is reflected back, and the light of the remaining wavelengths passes through the strong reflection grating 11 and is received by the photodetector 12 and converted into an electrical signal and uploaded to the data acquisition card 17. In this way, the reflection signal of the grating array at different wavelengths is obtained. The intensity of the signal reflected back by the chirped grating is different. By fitting these intensity values, the reflection spectrum of the chirped grating can be restored. The change of the temperature around the grating can be detected by the change of the reflection spectrum, and distributed temperature sensing can be realized.

[0061] The pulse light of the narrow linewidth laser 1 is reflected by the strong reflection grating 11 and then passes through the optical circulator 2 10 into an unbalanced Mach-Zehnder interferometer 13 (MZI) to be divided into two pulse lights. One arm of the unbalanced Mach-Zehnder interferometer 13 has a delay fiber, and there will be a certain delay when the two light pulses propagate along the two arms. When the length of the delay fiber of one arm of the unbalanced Mach-Zehnder interferometer 13 is 2L, the pulses reflected by the adjacent chirped fiber gratings will meet at the other end of the unbalanced Mach-Zehnder interferometer 13, thereby generating interference. The interference signal is divided into three paths with a phase difference of 120° through a 3×3 coupler. The three-path output optical signals are converted into electrical signals by three photoelectric detectors and uploaded to the data acquisition card 17 for data processing. The phase change of the interference signal is demodulated by the 3×3 coupler demodulation algorithm to restore the external vibration signal.

[0062] Figure 2 The reflection spectrum of a grating in the grating array is measured after it is heated in a high-temperature furnace. As the temperature increases, the spectrum of the grating drifts, and the drift of the spectrum has a good linear relationship with the change in temperature. By measuring the drift of the grating spectrum, the change in external temperature can be measured. Figure 3 The system collects the interference signal of a certain section of the grating array. The reflected pulses between adjacent gratings form a stable interference signal. The vibration signal can be restored by detecting the change in the phase of the interference signal. Figure 4The time domain and frequency domain spectra of the measured 90Hz sinusoidal signal show that the vibration signal is well restored.

[0063] The above is a detailed introduction to the distributed optical fiber sensing system and method for realizing simultaneous measurement of vibration and temperature provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0064] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A distributed optical fiber sensing system for simultaneous measurement of vibration and temperature, characterized in that: The invention comprises a narrow line width laser (1), a tunable laser (2) and a grating array (9); the lasers emitted by the narrow line width laser (1) and the tunable laser (2) are transmitted to a first optical circulator (8) after passing through a laser amplifier to obtain detection pulse light; the first optical circulator (8) is also connected to the grating array (9) and the second optical circulator (10); the second optical circulator (10) is connected to a strong reflection grating (11) and an unbalanced Mach-Zehnder interferometer (13); the strong reflection grating (11) and the unbalanced Mach-Zehnder interferometer (13) are both connected to a photoelectric detector; The optical circulator 1 (8) is used to input the detection pulse light from the first port and inject it into the grating array (9) from the second port, and the reflected light pulse of the grating array (9) is then output from the third port of the optical circulator 1 (8) to the optical circulator 2 (10); The optical circulator 2 (10) is used to input the reflected light pulse output by the optical circulator 1 (8) through the first port, and then output it from the second port of the optical circulator 2 (10) to the strong reflection grating (11), and the reflected pulse of the strong reflection grating (11) is output from the third port to the unbalanced Mach-Zehnder interferometer (13); The strong reflection grating (11) is used to reflect the detection pulse light of the narrow line width laser (1) through the detection pulse light of the tunable laser (2), and the reflected detection pulse light of the narrow line width laser (1) is output to the unbalanced Mach-Zehnder interferometer (13) through the third port of the second optical circulator (10); The unbalanced Mach-Zehnder interferometer (13) is used to generate interference between reflected pulses of adjacent gratings in the grating array (9), and output the interference light in phase to different photoelectric detectors.

2. The distributed optical fiber sensing system for realizing simultaneous vibration and temperature measurement according to claim 1, characterized in that: The narrow linewidth laser (1) is used to emit continuous high-coherence laser light; the tunable laser (2) is used to sequentially emit continuous frequency-sweeping laser light of different wavelengths.

3. The distributed optical fiber sensing system for realizing simultaneous measurement of vibration and temperature according to claim 1, characterized in that: The laser amplifier comprises a semiconductor laser amplifier 1 (3), a semiconductor laser amplifier 2 (4), a pulse signal generator (5) and an erbium-doped fiber amplifier (7); The semiconductor laser amplifier 1 (3) is connected to the pulse signal generator (5) and is used to modulate the continuous light output by the narrow linewidth laser (1) into a detection light pulse and output it to the optical fiber coupler (6); The semiconductor laser amplifier 2 (4) is connected to the pulse signal generator (5) and is used to modulate the continuous light output by the tunable laser (2) into a detection light pulse and output it to the optical fiber coupler (6); The optical fiber coupler (6) inputs the coupled detection light pulse into the erbium-doped optical fiber amplifier (7).

4. The distributed optical fiber sensing system for realizing simultaneous vibration and temperature measurement according to claim 1, characterized in that: The grating array (9) is a chirped fiber grating array, and adjacent gratings are arranged at a fixed interval.

5. The distributed optical fiber sensing system for realizing simultaneous vibration and temperature measurement according to claim 1, characterized in that: The strong reflection grating (11) is a narrow-band grating whose central wavelength is consistent with the wavelength of laser light emitted by the narrow-linewidth laser (1).

6. The distributed optical fiber sensing system for realizing simultaneous vibration and temperature measurement according to claim 1, characterized in that: One arm of the unbalanced Mach-Zehnder interferometer (13) is provided with a time-delay optical fiber with a length of 2L, where L is the spacing between adjacent gratings in the grating array; the pulsed light reflected by adjacent chirped fiber gratings generates interference in the unbalanced Mach-Zehnder interferometer (13), and the interference signal is divided into three signals with a phase difference of 120° through a 3×3 coupler, and the three signals are input into three photoelectric detectors.

7. A distributed optical fiber sensing method for a distributed optical fiber sensing system for realizing simultaneous measurement of vibration and temperature according to any one of claims 1 to 6, characterized in that: The steps include: The lasers emitted by the narrow line width laser (1) and the tunable laser (2) are amplified to obtain detection pulse light which is transmitted to an optical circulator (8); The optical circulator 1 (8) injects the detection pulse light into the grating array (9), and the reflected light pulse of the grating array (9) is then output to the optical circulator 2 (10) through the optical circulator 1 (8); The optical circulator 2 (10) injects the reflected light pulse output by the optical circulator 1 (8) into the strong reflection grating (11); The strong reflection grating (11) passes through the detection pulse light of the tunable laser (2) and outputs it to the photodetector 1 (12), thereby obtaining the reflection signals of the grating array (9) at different wavelengths, fitting the intensity values ​​of the reflection signals at different wavelengths, restoring the reflection spectrum of the grating array (9), detecting the temperature change around the grating array (9) through the change of the reflection spectrum, and realizing distributed temperature sensing; The strong reflection grating (11) reflects the detection pulse light of the narrow line width laser (1), and the reflected detection pulse light of the narrow line width laser (1) is output to the unbalanced Mach-Zehnder interferometer (13) via the second optical circulator (10); The unbalanced Mach-Zehnder interferometer (13) generates interference on reflected pulses of adjacent gratings in the grating array (9), and outputs the interference light in phase to different photodetectors, and restores the vibration signal around the grating array (9) by demodulating the phase change of the interference signal, thereby realizing distributed vibration sensing.

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