A distributed multi-parameter sensing system based on a multi-core optical fiber
By combining distributed fiber optic sensing technology using multi-core optical fibers and Rayleigh scattering, Raman scattering, and Brillouin scattering, and integrating phase-sensitive optical time-domain reflectometers, Raman optical time-domain reflectometers, and Brillouin optical time-domain reflectometers, the difficulties of signal crosstalk and decoupling in multi-parameter measurements in traditional fiber optic sensors are solved. This enables simultaneous and accurate measurement of temperature, vibration, and strain, improving measurement accuracy and system sensitivity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XI AN JIAOTONG UNIV
- Filing Date
- 2024-05-29
- Publication Date
- 2026-07-07
AI Technical Summary
Traditional distributed fiber optic sensing technology struggles to simultaneously and accurately measure multiple parameters such as temperature, vibration, and strain, and suffers from signal crosstalk and decoupling difficulties, affecting measurement accuracy and system sensitivity.
Distributed fiber optic sensing technology combining multi-core optical fibers with Rayleigh scattering, Raman scattering, and Brillouin scattering is employed. By integrating a phase-sensitive optical time-domain reflectometer, a Raman optical time-domain reflectometer, and a Brillouin optical time-domain reflectometer, signal separation and demodulation are performed using multi-core optical fibers, and data compensation is performed using a central processing unit, ultimately achieving simultaneous measurement of multiple parameters.
It achieves accurate simultaneous measurement of temperature, vibration, and strain, solves signal crosstalk and decoupling problems, and improves measurement accuracy and system sensitivity.
Smart Images
Figure CN118603152B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fiber optic sensing technology, and in particular to a distributed multi-parameter sensing system based on multi-core optical fiber. Background Technology
[0002] Fiber optic sensing technology is a new type of sensing technology that has gradually emerged alongside fiber optic technology and fiber optic communication technology. Fiber optic sensors possess characteristics such as corrosion resistance, electromagnetic interference resistance, high temperature resistance, and good electrical insulation, thus enabling their widespread application in various harsh environments. When light propagates in an optical fiber, various types of scattering, reflection, and transmission phenomena occur. Its wavelength, phase, intensity, and polarization state are affected by external environmental factors such as temperature, vibration, and pressure, causing changes. Therefore, by detecting and analyzing the optical characteristics of scattered, reflected, or transmitted light, it is possible to sense external physical quantities.
[0003] Compared to traditional electrical sensors and point-type fiber optic sensors, distributed fiber optic sensors offer advantages such as high capacity and long distance, long lifespan, and high cost-effectiveness. Distributed fiber optic sensing systems can directly utilize commercially produced fiber optics without requiring special internal structures; a single sensing fiber can serve as the transmission medium for multiple sensing units. Distributed fiber optic sensing technologies are mostly based on three scattering effects in optical fibers: Rayleigh scattering, Brillouin scattering, and Raman scattering. Rayleigh scattering has high backscattering power, a higher signal-to-noise ratio, and a fast response, and is typically used for measuring dynamic signals such as vibrations and sound waves. Brillouin scattering is sensitive to both temperature and strain; external temperature or strain sensing information can be obtained by demodulating changes in the Brillouin gain spectrum. Raman scattering is only sensitive to temperature; distributed temperature measurement can be achieved through self-demodulation techniques using anti-Stokes light or temperature demodulation techniques based on the ratio of Stokes light to anti-Stokes light, and is commonly used for distributed temperature sensing.
[0004] Traditional distributed fiber optic sensing technologies are mostly implemented within a single fiber, utilizing optical time-domain reflectometry or optical frequency-domain reflectometry to measure changes in single parameters such as temperature, strain, and vibration at different locations along the fiber. However, these measurements are limited by interference from other parameters. With the further development of distributed fiber optic sensing technology, its application scenarios have become increasingly complex and diverse. In some special environments, it is necessary to simultaneously and accurately measure changes in multiple parameters such as temperature, vibration, and strain. A single fiber core can only measure one set of data at a time, making simultaneous measurement of multiple parameters difficult. Integrating multiple sensing technologies into a single fiber core presents challenges such as crosstalk between signals and decoupling of multiple parameters, increasing detection difficulty, reducing the signal-to-noise ratio, and affecting measurement accuracy. Therefore, a new measurement method or sensing system is needed to meet the multi-parameter measurement requirements of distributed fiber optic sensing systems and achieve higher system sensitivity and measurement accuracy.
[0005] Patent application "A multi-core fiber optic distributed sensing system and measurement method"
[0006] (CN116539189A) employs Raman distributed fiber optic sensing technology to achieve distributed temperature and bending measurements. It utilizes a wavelength division multiplexer to split Raman scattered light into Stokes and anti-Stokes beams. Temperature data is demodulated using the anti-Stokes beam, and bending data is demodulated from the Stokes beam. However, this approach, which directly demodulates temperature from the anti-Stokes beam and equates bending loss to bending detection results, reduces the accuracy of temperature detection and bending measurement in the sensing system. Summary of the Invention
[0007] In order to overcome the shortcomings of the existing technology, the present invention aims to provide a distributed optical fiber sensing system based on multi-core optical fiber. By integrating three distributed optical fiber sensing technologies into multi-core optical fiber, crosstalk between temperature, vibration and strain is eliminated, and the three parameters can be measured accurately at the same time.
[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0009] A distributed multi-parameter sensing system based on multi-core optical fiber includes a laser 1. The laser 1 emits a laser source, which is driven by a trigger pulse input to a signal generator 9. The laser then interacts with a Rayleigh scattering-based phase-sensitive optical time-domain reflectometry (φ-OTDR) and its demodulation device 2, a Raman scattering-based Raman optical time-domain reflectometry (ROTDR) and its demodulation device 3, and a Brillouin optical time-domain reflectometry (BRI) based on Brillouin scattering. The signal input terminals of the phase-sensitive optical time-domain reflectometer (BOTDR) and its demodulation device 4 are connected to each other. The signal output terminals of the phase-sensitive optical time-domain reflectometer and its demodulation device 2, the Raman optical time-domain reflectometer and its demodulation device 3, and the Brillouin optical time-domain reflectometer and its demodulation device 4 are connected to the signal input terminals of the multi-core optical fiber 7 through the multi-core optical fiber fan-in fan-out module 5. The signal output terminals of the phase-sensitive optical time-domain reflectometer and its demodulation device 2, the Raman optical time-domain reflectometer and its demodulation device 3, and the Brillouin optical time-domain reflectometer and its demodulation device 4 are also connected to the central processing unit 6.
[0010] The Rayleigh scattering-based phase-sensitive optical time-domain reflectometer and its demodulation device 2 include a first acousto-optic modulator 2-1. The signal input terminal of the first acousto-optic modulator 2-1 is connected to the output terminal of the laser 1. The signal output terminal of the first acousto-optic modulator 2-1 is connected to the signal input terminal of the first optical amplifier 2-2. The signal output terminal of the first optical amplifier 2-2 is connected to the signal input terminal of the first circulator 2-3. The first signal output terminal of the first circulator 2-3 is connected to the signal input terminal of the multi-core fiber fan-in / fan-out module 5. The signal output port of the multi-core fiber fan-in / fan-out module 5 is connected to the multi-core fiber 7. The second signal output terminal of the first circulator 2-3 is connected to the signal input terminal of the first photodetector 2-4. The signal output terminal of the first photodetector 2-4 is connected to the signal input terminal of the central processing unit 6 through the data acquisition card 8.
[0011] The Raman scattering-based Raman optical time-domain reflectometer and its demodulation device 3 include a second acousto-optic modulator 3-1. The signal input terminal of the second acousto-optic modulator 3-1 is connected to the signal output terminal of the laser 1. The signal output terminal of the second acousto-optic modulator 3-1 is connected to the signal input terminal of the second optical amplifier 3-2. The signal output terminal of the second optical amplifier 3-2 is connected to the signal input terminal of the second circulator 3-3. The first signal output terminal of the second circulator 3-3 is connected to the signal input terminal of the multi-core fiber fan-in / fan-out module 5. The signal output port of the multi-core fiber fan-in / fan-out module 5 is connected to the multi-core fiber 7. The second signal output terminal of the second circulator 3-3 is connected to the signal input terminal of the wavelength division multiplexer 3-4. The signal output terminal of the wavelength division multiplexer 3-4 is connected to the signal input terminals of the second photodetector 3-5 and the third photodetector 3-6, respectively. The signal output terminals of the second photodetector 3-5 and the third photodetector 3-6 are connected to the signal input terminal of the central processing unit 6 through the data acquisition card 8.
[0012] The Brillouin optical time-domain reflectometer and its demodulation device 4 based on Brillouin scattering include an electro-optic modulator 4-1. The signal input terminal of the electro-optic modulator 4-1 is connected to the signal output terminal of the laser 1. The signal output terminal of the electro-optic modulator 4-1 is connected to the signal input terminal of the third optical amplifier 4-2. The signal output terminal of the third optical amplifier 4-2 is connected to the signal input terminal of the third circulator 4-3. The first signal output terminal of the third circulator 4-3 is connected to the signal input terminal of the multi-core fiber fan-in / fan-out module 5. The signal output port of the multi-core fiber fan-in / fan-out module 5 is connected to the multi-core fiber 7. The second signal output terminal of the third circulator 4-3 is connected to the signal input terminal of the fourth photodetector 4-4. The signal output terminal of the fourth photodetector 4-4 is connected to the signal input terminal of the central processing unit 6 through the data acquisition card 8.
[0013] The data acquisition card 8 has four channels, which respectively acquire Rayleigh scattering photoelectric signals 2-4 converted by the first photodetector, Stokes photoelectric signals converted by the second photodetector 3-5, anti-Stokes photoelectric signals converted by the third photodetector 3-6, and Brillouin scattering photoelectric signals acquired by the fourth photodetector 4-4.
[0014] The pulse signal output terminal of the signal generator 9 is also connected to four channels of the data acquisition card 8 to generate trigger pulses synchronized with the pulse light, so that the data acquisition card 8 can synchronously receive the Rayleigh scattering photoelectric signal 2-4 converted by the first photodetector, the Stokes photoelectric signal converted by the second photodetector 3-5, the anti-Stokes photoelectric signal converted by the third photodetector 3-6, and the Brillouin scattering photoelectric signal acquired by the fourth photodetector 4-4.
[0015] The multi-core optical fiber 7 has more than four cores. One or more cores are connected to the Rayleigh scattering phase-sensitive optical time-domain reflectometer and its demodulation device 2, one or more cores are connected to the Raman scattering Raman optical time-domain reflectometer and its demodulation device 3, and two symmetrical cores are connected to the BOTDR input module and demodulation device 4. The number of signal output ports of the multi-core optical fiber fan-in fan-out module 5 is adapted to the number of multi-core optical fibers 7.
[0016] The central processing unit 6 processes the received backscattered Rayleigh photoelectric signal to obtain external vibration information; the central processing unit 6 processes the received Stokes light and anti-Stokes photoelectric signals to obtain external temperature changes; the central processing unit 6 uses the received symmetrically distributed spontaneous Pyloric scattering data for bending compensation, uses the temperature change of Raman scattering light data to perform temperature compensation on the spontaneous Pyloric scattering data, and finally processes it to obtain strain measurement.
[0017] The first to third optical amplifiers are all pulsed optical amplifiers.
[0018] The laser 1 is a narrow-linewidth tunable continuous laser.
[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0020] 1. This invention uses multi-core optical fiber for sensing, with each core of the fiber serving as an independent sensing channel. It integrates distributed optical fiber sensing technologies based on Rayleigh scattering, Raman scattering, and Brillouin scattering to achieve simultaneous measurement of temperature, vibration, and strain.
[0021] 2. By employing Brillouin optical time-domain reflectometer technology on fiber cores symmetrically arranged in a multi-core optical fiber, the influence of optical cable bending on the measurement results of the sensing system was compensated.
[0022] 3. It solves the crosstalk problem between multiple physical quantity measurement signals in a single optical fiber in traditional optical fiber sensors, and avoids the energy loss problem caused by wavelength division multiplexing in the measurement of multiple physical quantities in a single fiber core.
[0023] 4. Based on spatial division multiplexing technology, multi-core optical fiber and fan-in / fan-out modules are used to separate Rayleigh scattering signals, Raman scattering signals and Brillouin scattering signals into independent channels for transmission and demodulation, which solves the problem of difficult decoupling of multi-parameter measurement signals in a single fiber core.
[0024] 5. Temperature compensation was performed on the strain measurement of the Brillouin optical time domain reflectometer and the vibration measurement of the phase-sensitive optical time domain reflectometer by temperature measurement of the Raman optical time domain reflectometer based on Raman scattering, thereby improving the measurement accuracy of the sensing system.
[0025] In summary, this invention utilizes multi-core optical fiber to integrate a phase-sensitive optical time-domain reflectometer, a Brillouin optical time-domain reflectometer, and a Raman optical time-domain reflectometer, enabling simultaneous measurement of temperature, vibration, and strain. The measurement accuracy of the sensing system is improved through bending self-compensation and temperature compensation techniques, and the signal decoupling difficulties of traditional fiber optic multi-parameter sensors are solved based on the spatial division multiplexing principle. Attached Figure Description
[0026] Figure 1 This is a schematic diagram of the optical fiber structure of the sensing system provided by the present invention, taking a seven-core optical fiber as an example.
[0027] Figure 2 This is a schematic diagram of the sensing system structure of the present invention.
[0028] Figure 3 This is a schematic diagram of a sensing system based on Rayleigh scattering phase-sensitive optical reflectometer (φ-OTDR) technology.
[0029] Figure 4 This is a schematic diagram of a sensing system based on Raman optical time domain reflectometer (ROTDR) technology.
[0030] Figure 5 This is a schematic diagram of a sensing system based on Brillouin Optical Time Domain Reflectometer (BOTDR) technology.
[0031] In the diagram: 1. Laser; 2. Phase-sensitive optical time-domain reflectometer and its demodulation device; 3. Raman optical time-domain reflectometer and its demodulation device; 4. Brillouin optical time-domain reflectometer and its demodulation device; 5. Multi-core fiber fan-in / fan-out module; 6. Central processing unit; 7. Multi-core fiber; 8. Data acquisition card; 9. Signal generator; 2-1. First acousto-optic modulator; 2-2. First optical amplifier; 2-3. First circulator; 2-4. First photodetector; 3-1. Second acousto-optic modulator; 3-2. Second optical amplifier; 3-3. Second circulator; 3-4. Wavelength division multiplexer; 3-5. Second photodetector; 3-6. Third photodetector; 4-1. Electro-optic modulator; 4-2. Third optical amplifier; 4-3. Third circulator; 4-4. Fourth photodetector. Detailed Implementation
[0032] The present invention will now be described in further detail with reference to the accompanying drawings.
[0033] Figure 1 The following is a schematic diagram of the optical fiber structure using a seven-core optical fiber as an example, referring to... Figure 1 In the seven-core fiber, Raman time-domain reflectometry (RTD) is applied in core ① to measure temperature changes. Brillouin time-domain interferometry (BDI) is applied in cores ② and ⑥. The temperature changes measured in core ① are used to correct the data measured by the Brillouin TRD and its demodulation device 4, thus measuring the strain on the fiber. The symmetrical arrangement of cores ② and ⑥ can compensate for measurement errors caused by bending. Rayleigh scattering phase-sensitive optical reflectometers are applied in core ⑦ to measure external vibrations. For other cores ③, ④, and ⑤, different schemes are flexibly selected according to the measurement environment and technical requirements. For example, Raman TRD is more commonly used in environments with complex temperatures, while Rayleigh scattering phase-sensitive optical reflectometers are more commonly used in environments with more complex vibrations. Averaging multiple sets of data improves measurement accuracy.
[0034] like Figure 2 As shown, since the system receives backscattered light signals, it adopts single-ended input and reception, meaning the signal generator and receiver are located on the same side. The system's phase-sensitive optical time-domain reflectometer and its demodulation device 2, Raman optical time-domain reflectometer and its demodulation device 3, and Brillouin optical time-domain reflectometer and its demodulation device 4 generate pulsed light signals of a certain frequency, which enter the input end of the multi-core fiber fan-in and fan-out module. Its output end is connected to one side of the multi-core fiber. External physical parameters act on the fiber. According to the scattering effect, the scattered signals are received from the system's incident end and demodulated. Each fiber core can obtain a set of sensing data. The demodulated data is processed and compensated by the central processing unit to obtain the measured quantities of external temperature, strain, and vibration.
[0035] A distributed multi-parameter sensing system based on multi-core optical fiber includes a laser 1. The laser 1 is a narrow-linewidth laser with a wavelength of 1550.12 nm. After being driven by a trigger pulse input from a signal generator 9, the laser is connected to the signal input terminals of a phase-sensitive optical time-domain reflectometer and its demodulation device 2 based on Rayleigh scattering, a Raman optical time-domain reflectometer and its demodulation device 3 based on Raman scattering, and a Brillouin optical time-domain reflectometer and its demodulation device 4 based on Brillouin scattering. The signal output terminals of the phase-sensitive optical time-domain reflectometer and its demodulation device 2, the Raman optical time-domain reflectometer and its demodulation device 3, and the Brillouin optical time-domain reflectometer and its demodulation device 4 are connected to the signal input terminals of the multi-core optical fiber through a multi-core optical fiber fan-in and fan-out module 5. The signal output terminals of the phase-sensitive optical time-domain reflectometer and its demodulation device 2, the Raman optical time-domain reflectometer and its demodulation device 3, and the Brillouin optical time-domain reflectometer and its demodulation device 4 are also connected to a central processing unit 6.
[0036] like Figure 3 As shown, the Rayleigh scattering-based phase-sensitive optical time-domain reflectometer and its demodulation device 2 include a first acousto-optic modulator 2-1. The signal input terminal of the first acousto-optic modulator 2-1 is connected to the output terminal of the laser 1. The signal output terminal of the first acousto-optic modulator 2-1 is connected to the signal input terminal of the first optical amplifier 2-2. The signal output terminal of the first optical amplifier 2-2 is connected to the signal input terminal of the first circulator 2-3. The first signal output terminal of the first circulator 2-3 is connected to the signal input terminal of the multi-core fiber fan-in / fan-out module 5. The signal output port of the multi-core fiber fan-in / fan-out module 5 is connected to the multi-core fiber 7. The second signal output terminal of the first circulator 2-3 is connected to the signal input terminal of the first photodetector 2-4. The signal output terminal of the first photodetector 2-4 is connected to the signal input terminal of the central processing unit 6 through the data acquisition card 8.
[0037] like Figure 4 As shown, the Raman optical time-domain reflectometer and its demodulation device 3 based on Raman scattering include a second acousto-optic modulator 3-1. The signal input terminal of the second acousto-optic modulator 3-1 is connected to the signal output terminal of the laser 1. The signal output terminal of the second acousto-optic modulator 3-1 is connected to the signal input terminal of the second optical amplifier 3-2. The signal output terminal of the second optical amplifier 3-2 is connected to the signal input terminal of the second circulator 3-3. The first signal output terminal of the second circulator 3-3 is connected to the signal input terminal of the multi-core fiber fan-in / fan-out module 5. The signal output port of the multi-core fiber fan-in / fan-out module 5 is connected to the multi-core fiber 7. The second signal output terminal of the second circulator 3-3 is connected to the signal input terminal of the wavelength division multiplexer 3-4. The signal output terminal of the wavelength division multiplexer 3-4 is connected to the signal input terminals of the second photodetector 3-5 and the third photodetector 3-6, respectively. The signal output terminals of the second photodetector 3-5 and the third photodetector 3-6 are connected to the signal input terminal of the central processing unit 6 through the data acquisition card 8.
[0038] like Figure 5 As shown, the Brillouin optical time-domain reflectometer and its demodulation device 4 based on Brillouin scattering include an electro-optic modulator 4-1. The signal input terminal of the electro-optic modulator 4-1 is connected to the signal output terminal of the laser 1. The signal output terminal of the electro-optic modulator 4-1 is connected to the signal input terminal of the third optical amplifier 4-2. The signal output terminal of the third optical amplifier 4-2 is connected to the signal input terminal of the third circulator 4-3. The first signal output terminal of the third circulator 4-3 is connected to the signal input terminal of the multi-core fiber fan-in / fan-out module 5. The signal output port of the multi-core fiber fan-in / fan-out module 5 is connected to the multi-core fiber 7. The second signal output terminal of the third circulator 4-3 is connected to the signal input terminal of the fourth photodetector 4-4. The signal output terminal of the fourth photodetector 4-4 is connected to the signal input terminal of the central processing unit 6 through the data acquisition card 8.
[0039] The data acquisition card 8 has four channels, which respectively acquire Rayleigh scattering photoelectric signals 2-4 converted by the first photodetector, Stokes photoelectric signals converted by the second photodetector 3-5, anti-Stokes photoelectric signals converted by the third photodetector 3-6, and Brillouin scattering photoelectric signals acquired by the fourth photodetector 4-4.
[0040] The pulse signal output terminal of the signal generator 9 is also connected to four channels of the data acquisition card 8 to generate trigger pulses synchronized with the pulse light, so that the data acquisition card 8 can synchronously receive the Rayleigh scattering photoelectric signal 2-4 converted by the first photodetector, the Stokes photoelectric signal converted by the second photodetector 3-5, the anti-Stokes photoelectric signal converted by the third photodetector 3-6, and the Brillouin scattering photoelectric signal acquired by the fourth photodetector 4-4.
[0041] The multi-core optical fiber 7 has more than four cores. One or more cores are connected to a Rayleigh scattering phase-sensitive optical time-domain reflectometer and its demodulation device 2, one or more cores are connected to a Raman scattering Raman optical time-domain reflectometer and its demodulation device 3, and two symmetrical cores are connected to a BOTDR input module and demodulation device 4.
[0042] The number of signal output ports of the multi-core fiber fan-in / fan-out module 5 is adapted to the number of multi-core fibers 7.
[0043] The central processing unit 6 processes the received backscattered Rayleigh photoelectric signal to obtain external vibration information; the central processing unit 6 processes the received Stokes light and anti-Stokes photoelectric signals to obtain external temperature changes; the central processing unit 6 uses the received symmetrically distributed spontaneous Brillouin scattering data for bending compensation, uses the temperature change of Raman scattering light data for temperature compensation of spontaneous Brillouin scattering data, and finally processes and demodulates to obtain strain measurement values.
[0044] To further explain the operation of the central processing unit 6, the system uses a ratio method to demodulate the temperature value from the Stokes light and anti-Stokes light collected by the system. The temperature value changes measured by the system are used to compensate for the temperature effects in the Brillouin scattered light and Rayleigh scattered light, thereby accurately demodulating the strain value. At the same time, the strain value measured by the system is used to compensate for the strain effects in the Rayleigh scattered light, thereby accurately demodulating the external vibration signal. The influence of fiber bending on the measured value is corrected by the symmetrically arranged Brillouin optical time domain reflectometer technology.
[0045] The laser 1 is a narrow linewidth tunable continuous laser.
[0046] The first to third optical amplifiers are pulsed light amplifiers; they are connected to port 1 of the modulator and the circulator to amplify the power of the pulsed light.
[0047] The signal generator 9 is used to input trigger pulses to the first acousto-optic modulator 2-1, the second acousto-optic modulator 3-1 and the electro-optic modulator 4-1, control the pulse width and repetition frequency of the optical pulses, and simultaneously connect to the signal acquisition card to generate a synchronous trigger signal.
[0048] The multi-core fiber fan-in / fan-out module 5 is used to couple optical signals into the multi-core fiber 7, and is selected according to the number of cores in the multi-core fiber 7.
[0049] The wavelength division multiplexer 3-4 is used to separate Stokes light and anti-Stokes light of different wavelengths in Raman scattered light.
[0050] The first to fourth photodetectors are used to convert the optical signals of the system into electrical signals, which are then acquired by the data acquisition card 8.
[0051] Compared with existing technologies, this invention makes full use of the characteristics of multi-core optical fibers. Since bending has opposite effects on two symmetrically arranged fiber cores, the average value obtained by taking advantage of this characteristic can compensate for the influence of optical cable bending on the system strain measurement. At the same time, the temperature measurement value is demodulated by the ratio method of Stokes light and anti-Stokes light. Therefore, this invention further improves the sensitivity and measurement accuracy of the system by using multi-core optical fibers to achieve multi-parameter measurement of temperature, strain, and vibration through temperature and bending compensation.
Claims
1. A distributed multi-parameter sensing system based on multi-core optical fiber, comprising a laser (1), characterized in that: The laser source emitted by the laser (1) is driven by the trigger pulse input from the signal generator (9) and then connected to the signal input terminals of the phase-sensitive optical time-domain reflectometer and its demodulation device (2) based on Rayleigh scattering, the Raman optical time-domain reflectometer and its demodulation device (3) based on Raman scattering, and the Brillouin optical time-domain reflectometer and its demodulation device (4) based on Brillouin scattering. The signal output terminals of the phase-sensitive optical time-domain reflectometer and its demodulation device (2), the Raman optical time-domain reflectometer and its demodulation device (3), and the Brillouin optical time-domain reflectometer and its demodulation device (4) are connected to the signal input terminal of the multi-core optical fiber (7) through the multi-core optical fiber fan-in and fan-out module (5). The signal output terminals of the phase-sensitive optical time-domain reflectometer and its demodulation device (2), the Raman optical time-domain reflectometer and its demodulation device (3), and the Brillouin optical time-domain reflectometer and its demodulation device (4) are also connected to the central processing unit (6). The multi-core optical fiber (7) The number of fiber cores is more than 4. One or more fiber cores are connected to the phase-sensitive optical time domain reflectometer and its demodulation device (2), one or more fiber cores are connected to the Raman optical time domain reflectometer and its demodulation device (3), and two symmetrical fiber cores are connected to the Brillouin optical time domain reflectometer input module and its demodulation device (4). The number of signal output ports of the multi-core fiber fan-in fan-out module (5) is adapted to the number of multi-core fibers (7). The central processing unit (6) demodulates the temperature value from the Stokes light and anti-Stokes light collected by the system using the ratio method. The temperature value change measured by the system is used to compensate for the temperature effect in the Brillouin scattered light and Rayleigh scattered light, thereby accurately demodulating the strain value. At the same time, the strain value measured by the system is used to compensate for the strain effect in the Rayleigh scattered light, thereby accurately demodulating the external vibration signal. The influence of fiber bending on the measured value is corrected by the symmetrically arranged Brillouin optical time domain reflectometer technology.
2. The distributed multi-parameter sensing system based on multi-core optical fiber according to claim 1, characterized in that: The Rayleigh scattering-based phase-sensitive optical time-domain reflectometer and its demodulation device (2) includes a first acousto-optic modulator (2-1), the signal input terminal of the first acousto-optic modulator (2-1) is connected to the output terminal of the laser (1), the signal output terminal of the first acousto-optic modulator (2-1) is connected to the signal input terminal of the first optical amplifier (2-2), the signal output terminal of the first optical amplifier (2-2) is connected to the signal input terminal of the first circulator (2-3), the first signal output terminal of the first circulator (2-3) is connected to the signal input terminal of the multi-core fiber fan-in fan-out module (5), and the signal output port of the multi-core fiber fan-in fan-out module (5) is connected to the multi-core fiber (7); the second signal output terminal of the first circulator (2-3) is connected to the signal input terminal of the first photodetector (2-4), and the signal output terminal of the first photodetector (2-4) is connected to the signal input terminal of the central processing unit (6) through the data acquisition card (8).
3. The distributed multi-parameter sensing system based on multi-core optical fiber according to claim 1, characterized in that: The Raman optical time-domain reflectometer and its demodulation device (3) based on Raman scattering includes a second acousto-optic modulator (3-1). The signal input terminal of the second acousto-optic modulator (3-1) is connected to the signal output terminal of the laser (1). The signal output terminal of the second acousto-optic modulator (3-1) is connected to the signal input terminal of the second optical amplifier (3-2). The signal output terminal of the second optical amplifier (3-2) is connected to the signal input terminal of the second circulator (3-3). The first signal output terminal of the second circulator (3-3) is connected to the signal input terminal of the multi-core fiber fan-in / fan-out module (5). The signal output port of the multi-core fiber fan-in / fan-out module (5) is connected to the multi-core fiber (7); the second signal output end of the second circulator (3-3) is connected to the signal input end of the wavelength division multiplexer (3-4), the signal output end of the wavelength division multiplexer (3-4) is connected to the signal input ends of the second photodetector (3-5) and the third photodetector (3-6) respectively, and the signal output ends of the second photodetector (3-5) and the third photodetector (3-6) are connected to the signal input end of the central processing unit (6) through the data acquisition card (8).
4. A distributed multi-parameter sensing system based on multi-core optical fiber according to claim 1, characterized in that: The Brillouin optical time-domain reflectometer and its demodulation device (4) based on Brillouin scattering includes an electro-optic modulator (4-1). The signal input terminal of the electro-optic modulator (4-1) is connected to the signal output terminal of the laser (1). The signal output terminal of the electro-optic modulator (4-1) is connected to the signal input terminal of the third optical amplifier (4-2). The signal output terminal of the third optical amplifier (4-2) is connected to the signal input terminal of the third circulator (4-3). The first signal output terminal of the third circulator (4-3) is connected to the signal input terminal of the multi-core fiber fan-in fan-out module (5). The signal output port of the multi-core fiber fan-in fan-out module (5) is connected to the multi-core fiber (7). The second signal output terminal of the third circulator (4-3) is connected to the signal input terminal of the fourth photodetector (4-4). The signal output terminal of the fourth photodetector (4-4) is connected to the signal input terminal of the central processing unit (6) through the data acquisition card (8).
5. A distributed multi-parameter sensing system based on multi-core optical fiber according to any one of claims 2 to 4, characterized in that: The data acquisition card (8) has four channels, which respectively acquire the Rayleigh scattering photoelectric signal converted by the first photodetector (2-4), the Stokes photoelectric signal converted by the second photodetector (3-5), the anti-Stokes photoelectric signal converted by the third photodetector (3-6), and the Brillouin scattering photoelectric signal acquired by the fourth photodetector (4-4).
6. A distributed multi-parameter sensing system based on multi-core optical fiber according to claim 1, characterized in that: The pulse signal output terminal of the signal generator (9) is also connected to the four channels of the data acquisition card (8) to generate trigger pulses synchronized with the pulse light, so that the data acquisition card (8) can synchronously receive the Rayleigh scattering photoelectric signal (2-4) converted by the first photodetector, the Stokes photoelectric signal converted by the second photodetector (3-5), the anti-Stokes photoelectric signal converted by the third photodetector (3-6), and the Brillouin scattering photoelectric signal acquired by the fourth photodetector (4-4).
7. A distributed multi-parameter sensing system based on multi-core optical fiber according to any one of claims 2 to 4, characterized in that: The first, second, and third optical amplifiers all employ pulsed optical amplifiers.
8. A distributed multi-parameter sensing system based on multi-core optical fiber according to claim 1, characterized in that: The laser (1) is a narrow linewidth tunable continuous laser.