Measurement system

Abstract

This application provides a measurement system comprising: a first sensing fiber, a second sensing fiber, and a processing module; acquiring a first reference light and a second reference light, and a first probe light and a second probe light of the sensing fiber under test; the first sensing fiber receiving the first probe light and the first reference light to generate a first back-blown Brillouin scattering signal; the second sensing fiber receiving the second probe light and the second reference light to generate a second back-blown Brillouin scattering signal; and the processing module determining whether the first back-blown Brillouin scattering signal and the second back-blown Brillouin scattering signal are consistent to determine whether the change in the sensing fiber under test is caused by temperature or strain. This application, by setting up a first sensing fiber, a second sensing fiber, and a processing module, solves the problems of inaccurate temperature and strain measurements and slow measurement speed in existing technologies, achieving simultaneous measurement of temperature and strain at various points on the sensing fiber under test, and accelerating the measurement speed.

Description

Technical Field

[0001] This application relates to the field of computer technology, and more particularly to a measurement system. Background Technology

[0002] Fiber optic sensing technology emerged in the 1970s. It uses light as the carrier and optical fiber as the sensing medium, obtaining relevant physical quantities by measuring optical parameters. Fiber optic sensors based on BOTDA (Brillouin Optical Time Domain Analysis) are an important branch of distributed sensors. Compared with traditional sensors, they have advantages such as long transmission distance, high positioning accuracy, and strong anti-interference capabilities, and are widely used in submarine cable monitoring, rail transportation, oil and gas pipelines, and military applications.

[0003] In existing technologies, "LEAF fiber" is combined with the BOTDA system. The fiber Brillouin gain spectrum in LEAF has multiple gain peaks. Temperature and strain are measured based on the different coefficients between the frequency shift of each peak and temperature and strain.

[0004] However, in existing technologies, measuring temperature and strain separately is not feasible because of the cross-sensitivity between temperature and strain. This makes it difficult to effectively distinguish which factor caused the signal change, resulting in inaccurate temperature and strain measurements. Summary of the Invention

[0005] The main objective of this invention is to provide a measurement system that addresses the technical problems in the prior art where, when measuring temperature or strain alone, the measured temperature and strain results are inaccurate and the measurement speed is slow due to the cross-sensitivity between temperature and strain.

[0006] In a first aspect, this application provides a measurement system, the measurement system comprising:

[0007] A first sensing fiber, a second sensing fiber, and a processing module; wherein the first sensing fiber is sensitive to temperature or strain; and the second sensing fiber is sensitive to temperature and / or strain.

[0008] Acquire the first and second reference beams, and the first and second probe beams of the optical fiber under test;

[0009] The first sensing fiber receives the first probe light and the first reference light, and generates the first back-brillouin scattering light signal.

[0010] The second sensing fiber receives the second probe light and the second reference light, and generates a second back-brillouin scattering light signal.

[0011] The processing module determines whether the first back-blown Brillouin scattered light signal and the second back-blown Brillouin scattered light signal are consistent, thus determining that the change in the sensing fiber under test is caused by temperature or strain.

[0012] Furthermore, the measurement system also includes: a processing module;

[0013] The processing module determines whether the first backscattered Brillouin light signal and the second backscattered Brillouin light signal are consistent, thus determining that the change in the sensing fiber under test is caused by temperature or strain, specifically including:

[0014] When the first sensing fiber is sensitive to temperature, and the processing module detects that the first backscattered Brillouin light signal and the second backscattered Brillouin light signal are consistent, it is determined that the sensing fiber under test is affected by temperature.

[0015] When the first sensing fiber is sensitive to temperature, and the processing module detects that the first backscattered Brillouin light signal and the second backscattered Brillouin light signal are inconsistent, it is determined that the sensing fiber under test is changed by strain.

[0016] When the first sensing fiber is sensitive to strain, and the processing module detects that the first backscattered Brillouin light signal and the second backscattered Brillouin light signal are consistent, it is determined that the sensing fiber under test is changed by strain.

[0017] If the first sensing fiber is sensitive to strain, and the processing module detects that the first backscattered Brillouin light signal and the second backscattered Brillouin light signal are inconsistent, then it is determined that the sensing fiber under test is affected by temperature changes.

[0018] Furthermore, the measurement system also includes: a laser, a first coupler, an electro-optic modulation module, a filtering module, and a third coupler;

[0019] Acquiring the first and second reference beams, and the first and second probe beams of the fiber optic cable under test, specifically includes:

[0020] The laser emits a continuous, narrow-linewidth light source to the first coupler;

[0021] The first coupler splits the narrow linewidth light source into a first optical signal and a second optical signal according to a first preset ratio; and inputs the first optical signal to the electro-optic modulation module;

[0022] The electro-optic modulation module is used to shift the frequency of the detection optical signal and connect it to the optical fiber under test. The output detection light of the optical fiber is then connected to the filtering module.

[0023] The filtering module obtains the preset wavelength in the output probe light and filters out the remaining wavelengths, and then outputs the output probe light to the third coupler;

[0024] The third coupler splits the output probe light into a first probe light and a second probe light according to a second preset ratio, thereby obtaining the first probe light and the second probe light of the sensing fiber under test.

[0025] Furthermore, the measurement system also includes: a pulse modulation module and a second coupler;

[0026] Acquiring the first and second reference beams, and the first and second probe beams of the fiber optic cable under test, specifically also includes:

[0027] The second optical signal is input to the pulse modulation module, which performs pulse modulation on the second optical signal and outputs the modulated and amplified pulsed light to the second coupler.

[0028] The second coupler divides the modulated and amplified pulsed light into a first reference light and a second reference light according to a third preset ratio, thus obtaining the reference light and the second reference light.

[0029] Furthermore, the measurement system also includes: a first circulator and a second circulator;

[0030] The first circulator has a first port, a second port, and a third port;

[0031] The first reference light is input to the first port of the first circulator and output to the first sensing fiber through the second port of the first circulator.

[0032] The first probe light is input to the first sensing fiber;

[0033] The first sensing fiber generates a first back-brillouin scattered light signal and outputs it to the processing module through the third port of the first circulator.

[0034] The second circulator has a first port, a second port, and a third port;

[0035] The second reference light is input to the first port of the second circulator and output to the second sensing fiber through the second port of the second circulator.

[0036] The second probe light is input to the second sensing fiber;

[0037] The second sensing fiber generates a second back-scattered Brillouin light signal, which is then output to the processing module through the third port of the second circulator.

[0038] Furthermore, the processing module specifically includes: an optoelectronic differential module and a data processing module;

[0039] When the photoelectric differential module detects that the output information of the third port of the first circulator is consistent with the output information of the third port of the second circulator, it determines that the temperature or strain has caused a change in the optical fiber under test.

[0040] When the photoelectric differential module detects that the output information of the third port of the first circulator is inconsistent with the output information of the third port of the second circulator, it determines that the strain or temperature has caused a change in the fiber optic sensor under test.

[0041] The data processing module determines the temperature and stress distribution at various points in the optical fiber under test based on the output of the optoelectronic differential module and the relationship between Brillouin frequency shift, strain, and temperature.

[0042] Furthermore, the optoelectronic differential module specifically includes:

[0043] A first avalanche photodiode, a second avalanche photodiode, and an amplifier; wherein the first and second avalanche photodiodes have opposite polarities; used for differential processing of optical signals;

[0044] The first avalanche photodiode receives the first output optical signal from the third port of the first circulator; the second avalanche photodiode receives the second output optical signal from the third port of the second circulator.

[0045] The amplifier receives the differential first and second output optical signals and amplifies them.

[0046] Furthermore, the pulse modulation module specifically includes: an acousto-optic modulator, a first erbium-doped fiber amplifier, and a polarization scrambler;

[0047] The acousto-optic modulator receives the second optical signal and modulates it into a pulsed optical signal.

[0048] The first erbium-doped fiber amplifier amplifies the power of the pulsed optical signal to obtain the amplified pulsed optical signal;

[0049] The polarization scrambler is used to correct the amplified pulsed light signal to obtain a corrected pulsed light signal.

[0050] Furthermore, the electro-optic modulation module specifically includes:

[0051] Electro-optic modulator and second erbium-doped fiber amplifier;

[0052] An electro-optic modulator receives a first optical signal and periodically modulates the optical frequency of the first optical signal to obtain a modulated optical signal.

[0053] The second erbium-doped fiber amplifier amplifies the power of the modulated optical signal to obtain the amplified optical signal.

[0054] Furthermore, the first sensing fiber includes a loosely fitted sensing fiber, and the second sensing fiber includes a tightly fitted sensing fiber.

[0055] This application provides a measurement system comprising: a first sensing fiber, a second sensing fiber, and a processing module; wherein the first sensing fiber is sensitive to temperature or strain; the second sensing fiber is sensitive to temperature and / or strain; the system acquires a first reference light and a second reference light, and a first probe light and a second probe light of the sensing fiber under test; the first sensing fiber receives the first probe light and the first reference light to generate a first backscattered Brillouin light signal; the second sensing fiber receives the second probe light and the second reference light to generate a second backscattered Brillouin light signal; the processing module determines whether the first backscattered Brillouin light signal and the second backscattered Brillouin light signal are consistent, thereby determining that the change in the sensing fiber under test is caused by temperature or strain. This application, by setting up a first sensing fiber and a second sensing fiber, identifies the variable causing the change in the sensing fiber under test, and uses the processing module to determine the temperature and stress distribution at various points in the sensing fiber under test. This invention addresses the problem of inaccurate temperature and strain measurements and slow measurement speed caused by the cross-sensitivity between temperature and strain in existing technologies. It enables simultaneous measurement of temperature and strain at various points on the sensing fiber under test, and accelerates the measurement speed. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0057] Figure 1 A schematic diagram of a measurement system provided in an embodiment of this application;

[0058] Figure 2 This is a schematic diagram of another measurement system provided in an embodiment of this application.

[0059] Explanation of icon numbers:

[0060]

[0061]

[0062] The accompanying drawings have illustrated specific embodiments of this disclosure, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concepts of this disclosure to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0063] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0064] Fiber optic sensing technology emerged in the 1970s. It uses light as the carrier and optical fiber as the sensing medium, obtaining relevant physical quantities by measuring optical parameters. Fiber optic sensors based on BOTDA (Brillouin Optical Time Domain Analysis) are an important branch of distributed sensors. Compared with traditional sensors, they have advantages such as long transmission distance, high positioning accuracy, and strong anti-interference capabilities, and are widely used in submarine cable monitoring, rail transportation, oil and gas pipelines, and military applications.

[0065] In existing technologies, "LEAF fiber" is combined with the BOTDA system. The fiber Brillouin gain spectrum in LEAF has multiple gain peaks. Temperature and strain are measured based on the different coefficients between the frequency shift of each peak and temperature and strain.

[0066] However, in existing technologies, measuring temperature and strain separately is not feasible because of the cross-sensitivity between temperature and strain. This makes it difficult to effectively distinguish which factor caused the signal change, resulting in inaccurate temperature and strain measurements.

[0067] To address the aforementioned problems, this application provides a measurement system aimed at solving the technical issues in the prior art where, when measuring temperature or strain individually, the cross-sensitivity of temperature and strain leads to inaccurate measurement results and slow measurement speed. The technical concept of this application is as follows: by setting up a first sensing fiber, a second sensing fiber, and a processing module, since the first sensing fiber is sensitive to temperature or strain, and the second sensing fiber is sensitive to temperature and / or strain, the processing module determines whether the first backscattered Brillouin light signal and the second backscattered Brillouin light signal generated by the first and second sensing fibers are consistent, thus determining that the change in the sensing fiber under test is caused by temperature or strain. This solves the problem in the prior art where the cross-sensitivity of temperature and strain leads to inaccurate measurement results and slow measurement speed, enabling simultaneous measurement of temperature and strain at various points on the sensing fiber under test, and accelerating the measurement speed.

[0068] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0069] Example 1

[0070] Figure 1 The measurement system provided in Embodiment 1 of this application. For example... Figure 1 As shown, the measurement system 10 provided in this embodiment includes a laser 101, a first coupler 102, an electro-optic modulation module 103, a pulse modulation module 104, a second coupler 105, a first circulator 106, a second circulator 107, a first sensing fiber 108, a second sensing fiber 109, a third coupler 110, a filtering module 111, and a processing module 112.

[0071] Laser 101 is used to emit a continuous light source. Due to the outstanding advantages of semiconductor lasers, such as high energy conversion efficiency, ease of high-speed current modulation, ultra-miniaturization, simple structure, and long service life, a semiconductor laser is selected in this embodiment. The wavelength coverage of the semiconductor laser is from ultraviolet to infrared (300nm to tens of micrometers), with 1.3µm and 1.55µm being two windows for fiber optic transmission. Semiconductor lasers are used in Gb local area networks. Alternatively, a digital laser can be selected, in which one of the reflectors is replaced with a "spatial light modulator." The "spatial light modulator" is like a reflective miniature liquid crystal display screen; "the desired laser mode can be obtained simply by inputting a specific image to the display screen via a computer."

[0072] The first coupler 102 is used to split the light source into two paths according to a certain ratio. In this embodiment, an optocoupler can be selected. An optocoupler is an electro-optical-electrical conversion device that transmits electrical signals using light as a medium. An optocoupler consists of a light source and a light receiver. The light source and the light receiver are assembled in the same sealed housing and isolated from each other by a transparent insulator. The pins of the light source are the input terminals, and the pins of the light receiver are the output terminals. Common light sources are light-emitting diodes (LEDs), and common light receivers are photodiodes or phototransistors. A coupler is a radio frequency device that extracts a small portion of the signal from the main wireless signal channel. Unlike other devices, a coupler is a power distribution device that distributes power unequally. Couplers are used in conjunction with power dividers primarily to achieve one goal—to distribute the transmission power of the signal source as evenly as possible to the next receiver, ensuring that the transmission power of each receiver is essentially the same.

[0073] The electro-optic modulation module 103 is used to shift the frequency of the continuous detection optical signal. It integrates an electro-optic intensity modulator and a bias point control circuit. The bias point control circuit uses external dithering to solve the problem that the modulation performance of the electro-optic intensity modulator is affected by the external environment, ensuring that the electro-optic modulator can work stably for a long time.

[0074] The pulse modulation module 104 is a pulse modulation module that uses a semiconductor optical amplifier (SOA) as the core conversion device to realize the generation of ultra-narrow pulse width optical pulses. Its fast rise time, high pulse extinction ratio, good stability and easy use make it an ideal choice to replace electro-optic and acousto-optic modulators in various fiber optic sensing systems.

[0075] The second coupler 105 is used to split the light source into two paths according to a certain ratio. In this embodiment, an optocoupler can be selected. An optocoupler is an electro-optical-electrical conversion device that transmits electrical signals using light as a medium. An optocoupler consists of a light source and a light receiver. The light source and the light receiver are assembled in the same sealed housing and isolated from each other by a transparent insulator. The pins of the light source are the input terminals, and the pins of the light receiver are the output terminals. Common light sources are light-emitting diodes (LEDs), and common light receivers are photodiodes or phototransistors. A coupler is a radio frequency device that extracts a small portion of the signal from the main wireless signal channel. Unlike other devices, a coupler is a power distribution device that distributes power unequally. Couplers are used in conjunction with power dividers primarily to achieve one goal—to distribute the transmission power of the signal source as evenly as possible to the next receiver, ensuring that the transmission power of each receiver is essentially the same.

[0076] The filtering module 111 is used to selectively acquire specific wavelengths in the optical signal and transmit the filtered optical signal to the third coupler 110.

[0077] The third coupler 1110 is used to split the light source into two paths according to a certain ratio. In this embodiment, an optocoupler can be selected. An optocoupler is an electro-optical-electrical conversion device that transmits electrical signals using light as a medium. An optocoupler consists of a light source and a light receiver. The light source and the light receiver are assembled in the same sealed housing and isolated from each other by a transparent insulator. The pins of the light source are the input terminals, and the pins of the light receiver are the output terminals. Common light sources are light-emitting diodes (LEDs), and common light receivers are photodiodes or phototransistors. A coupler is a radio frequency device that extracts a small portion of the signal from the main wireless signal channel. Unlike other devices, a coupler is a power distribution device that distributes power unequally. Couplers are used in conjunction with power dividers primarily to achieve one goal—to distribute the transmission power of the signal source as evenly as possible to the next receiver, ensuring that the transmission power of each receiver is essentially the same.

[0078] The first circulator 106 is used for unidirectional transmission of optical signals. The first circulator 106 is a multi-port device that transmits incident waves entering any port of the first circulator 106 to the next port in a sequential direction determined by the static bias magnetic field. It is a non-reversible device with multiple terminals, characterized by its ability to unidirectionally transmit high-frequency signal energy.

[0079] The second circulator 107 is used for unidirectional transmission of optical signals. The second circulator 107 is a multi-port device that transmits incident waves entering any port of the second circulator 107 to the next port in a sequential direction determined by the static bias magnetic field. It is a non-reversible device with multiple terminals, characterized by its ability to unidirectionally transmit high-frequency signal energy.

[0080] The first sensing fiber 108 is used to measure temperature by sensing and transmitting optical signals through optical fibers, and converting them into the physical quantity to be measured.

[0081] The second sensing fiber 109 is used to measure temperature and strain, transmitting optical signals via optical fibers and converting them into the physical quantity to be measured.

[0082] The processing module 112 is used to process the optical signal to determine whether the change in the optical fiber under test is caused by temperature or strain.

[0083] In the above technical solution, by setting up a first sensing fiber 108, a second sensing fiber 109 and a processing module 112, the problem of inaccurate temperature and strain measurement results and slow measurement speed caused by the cross-sensitivity of temperature and strain when measuring temperature or strain in the prior art is solved. The solution realizes simultaneous measurement of temperature and strain at various points of the sensing fiber under test and speeds up the measurement.

[0084] Example 2

[0085] Figure 2 This is the measurement system provided in Embodiment 2 of this application. For example... Figure 2 As shown, the measurement system 10 provided in this embodiment includes a laser 101, a first coupler 102, an electro-optic modulator 1031, a first erbium-doped fiber amplifier 1032, an acousto-optic modulator 1041, a second erbium-doped fiber amplifier 1042, a polarizer 1043, a second coupler 105, a first circulator 106, a second circulator 107, a loosely fitted sensing fiber 1081, a tightly fitted sensing fiber 1091, a third coupler 110, a filter module 111, an optoelectronic differential module 1121, a first avalanche photodiode 11211, a second avalanche photodiode 11212, an amplifier 11213, and a data processing module 1122.

[0086] In this embodiment, laser 101 emits a continuous narrow-linewidth light source and delivers it to the first coupler 102. Semiconductor lasers are selected in this embodiment due to their high energy conversion efficiency, ease of high-speed current modulation, miniaturization, simple structure, and long lifespan. The wavelength range of the semiconductor laser is from ultraviolet to infrared (300nm to tens of micrometers), with 1.3µm and 1.55µm serving as two windows for fiber optic transmission. Semiconductor lasers are used in Gb local area networks. Alternatively, a digital laser can be used, where one of the reflectors is replaced with a "spatial light modulator." The "spatial light modulator" functions like a reflective miniature liquid crystal display screen; the required narrow-linewidth light source can be obtained simply by inputting a specific image onto the screen via a computer.

[0087] The first coupler 102 is used to receive the narrow-linewidth light source emitted by the laser 101 and split the narrow-linewidth light source into two light paths at a 1:1 ratio. The first light signal is output as probe light to the electro-optic modulation module 103, and the second light signal is output as intrinsic light to the pulse modulation module 104. In this embodiment, an optocoupler can be selected as the first coupler 102, which consists of a light source and a light receiver. The light source and the light receiver are assembled in the same sealed housing and isolated from each other by a transparent insulator. The pins of the light source are the input terminals, and the pins of the light receiver are the output terminals. The light source is a light-emitting diode, and the light receiver is a photodiode. The first coupler 102 is a radio frequency device that extracts a small portion of the signal from the narrow-linewidth light source emitted by the laser 101. The first coupler 102 is used to ensure that the emission power of the narrow-linewidth light source emitted by the laser 101 is evenly distributed to the electro-optic modulation module 103 and the pulse modulation module 104, so that the power of the electro-optic modulation module 103 and the pulse modulation module 104 is the same.

[0088] The electro-optic modulation module 103 is used to frequency-shift the first reference optical signal generated by the first coupler 102 and transmit the frequency-shifted optical signal to the sensing fiber 20 under test. The electro-optic modulation module 103 integrates an electro-optic modulator 1031 and a first erbium-doped fiber amplifier 1032. The electro-optic modulator 1031 applies a voltage to the electro-optic crystal, causing a change in the optical wave characteristics of the electro-optic crystal, thereby modulating the phase, amplitude, intensity, and polarization state of the first reference optical signal. The electro-optic modulator 1031 receives the first reference optical signal generated by the first coupler 102 and frequency-shifts the first reference optical signal generated by the first coupler 102 to a pump pulse approximately equal to the Brillouin frequency shift. The frequency-shifted optical signal is then amplified by the first erbium-doped fiber amplifier 1032 and transmitted to the sensing fiber 20 under test. The first erbium-doped fiber amplifier 1032 is used as a power amplifier, located after the electro-optic modulator 1031. It is used to boost the power of multiple wavelength signals after multiplexing before transmission. Since the power of the signal after multiplexing is generally large, the noise figure and gain requirements of the power amplifier are not very high, but it is required to have a relatively large output power after amplification.

[0089] The pulse modulation module 104 is used to pulse-modulate the second reference optical signal generated by the first coupler 102 to achieve distributed measurement, and outputs the modulated and amplified pulsed light to the second coupler 105. The pulse modulation module 104 integrates an acousto-optic modulator 1041, a second erbium-doped fiber amplifier 1042, and a polarization scrambler 1043. The acousto-optic modulator 1041 receives the second optical signal and modulates it into a pulsed optical signal. The acousto-optic modulator 1041 modulates the second optical signal into a pulsed optical signal by controlling the change in laser beam intensity. The pulsed optical signal is then amplified by the second erbium-doped fiber amplifier 1042, which acts as a power amplifier. After the electro-optic modulator 1031, the power of the multiple wavelength signals after multiplexing is boosted before transmission. Since the power of the signal after multiplexing is generally large, the noise figure and gain requirements of the power amplifier are not very high, but a relatively large output power is required after amplification. The pulsed light after power amplification is then connected to the polarizer 1043. The NOPS series high-speed polarizer can be selected as the polarizer 1043. The NOPS series high-speed polarizer is a polarizer based on the fast phase delay function of the wave disk.

[0090] The second coupler 105 receives the modulated pulsed light sent by the pulse modulation module 104 and splits the modulated pulsed light into two paths at a 1:1 ratio. The first reference light signal is output to the first port of the first circulator 106, and the second reference light signal is output to the first port of the second circulator 107. In this embodiment, an optocoupler can be selected as the second coupler 105. The second coupler 105 consists of a light source and a light receiver. The light source and the light receiver are assembled in the same sealed housing and isolated from each other by a transparent insulator. The pins of the light source are the input terminals, and the pins of the light receiver are the output terminals. The light source is a light-emitting diode, and the light receiver is a photodiode. The second coupler 105 is a radio frequency device that extracts a small portion of the signal from the modulated pulsed light sent by the pulse modulation module 104. The second coupler 105 is designed to ensure that the transmission power of the modulated pulsed light sent by the pulse modulation module 104 is evenly distributed to the first circulator 106 and the second circulator 107, so that the power of the first circulator 106 and the second circulator 107 is the same.

[0091] The filtering module 111 is used to selectively acquire a specific wavelength of the optical signal output by the optical fiber under test 20 and transmit the filtered detection optical signal to the third coupler 110.

[0092] The third coupler 110 receives the filtered detection light signal sent by the filtering module 111 and splits the filtered detection light signal into two paths at a 1:1 ratio. The first detection light signal is output to the first sensing fiber 108, and the second detection light signal is output to the second sensing fiber 109. In this embodiment, an optocoupler can be selected as the third coupler 110. The third coupler 110 consists of a light source and a light receiver. The light source and the light receiver are assembled in the same sealed housing and isolated from each other by a transparent insulator. The pins of the light source are the input terminals, and the pins of the light receiver are the output terminals. The light source is a light-emitting diode, and the light receiver is a photodiode. Specifically, the third coupler 110 is a radio frequency device that extracts a small portion of the signal from the filtered probe light signal sent by the filter module 111. The third coupler 110 is designed to ensure that the transmission power of the filtered probe light signal sent by the filter module 111 is evenly distributed to the first sensing fiber 108 and the second sensing fiber 109, so that the power of the first sensing fiber 108 and the second sensing fiber 109 is the same.

[0093] The first circulator 106 is provided with a first port, a second port and a third port; the first port of the first circulator 106 is connected to the first reference light sent by the second coupler 105, and then the first reference light of the first port of the first circulator 106 is transmitted to the second port of the first circulator 106 through the static polarization magnetic field, and output to the first sensing fiber 108.

[0094] The second circulator 107 is provided with a first port, a second port and a third port; the first port of the second circulator 107 is connected to the second reference light sent by the second coupler 105, and then the first reference light of the first port of the second circulator 107 is transmitted to the second port of the second circulator 107 through the static polarization magnetic field, and output to the second sensing fiber 109.

[0095] The first sensing fiber 108 is sensitive to temperature or strain and is used to measure temperature or strain. Specifically, the first sensing fiber 108 receives the first probe light transmitted from the third coupler 110 and the output reference light from the second port of the first circulator 106, and generates a first back-blown Brillouin scattered light. This first back-blown Brillouin scattered light is then transmitted to the third port of the first circulator 106. The first sensing fiber 108 can be a loosely fitted sensing fiber 1081.

[0096] The second sensing fiber 109 is sensitive to temperature and / or strain and is used to measure temperature and / or strain. Specifically, the second sensing fiber 109 receives the second probe light transmitted by the third coupler 110 and the output reference light from the second port of the second circulator 107, and generates a second back-blown Brillouin scattered light. This second back-blown Brillouin scattered light is then transmitted to the third port of the second circulator 106. The second sensing fiber 108 can be a tight-buffered sensing fiber 1091.

[0097] Processing module 112 integrates optoelectronic differential module 1121 and data processing module 1122. Optoelectronic differential module 1121 integrates a first avalanche photodiode 11211, a second avalanche photodiode 11212, and an amplifier 11213. The first and second avalanche photodiodes have opposite polarities. The first avalanche photodiode 11211 receives the first back-scattered Brillouin light output from the third port of the first circulator 106. The second avalanche photodiode receives the second back-scattered Brillouin light output from the third port of the second circulator 107. Differential processing is performed on the first and second back-scattered Brillouin lights to suppress zero-point drift and remove common-mode noise. When the first sensing fiber is temperature-sensitive, and the optoelectronic differential module 1121 detects the first... If the first back-brillouin scattered light signal and the second back-brillouin scattered light signal are consistent, it is determined that the change in the sensing fiber under test is caused by temperature. If the first sensing fiber is sensitive to temperature and the photoelectric differential module 1121 detects that the first back-brillouin scattered light signal and the second back-brillouin scattered light signal are inconsistent, it is determined that the change in the sensing fiber under test is caused by strain. If the first sensing fiber is sensitive to strain and the photoelectric differential module 1121 detects that the first back-brillouin scattered light signal and the second back-brillouin scattered light signal are consistent, it is determined that the change in the sensing fiber under test is caused by strain. If the first sensing fiber is sensitive to strain and the photoelectric differential module 1121 detects that the first back-brillouin scattered light signal and the second back-brillouin scattered light signal are inconsistent, it is determined that the change in the sensing fiber under test is caused by temperature. The photoelectric differential module 1121 identifies the variable that causes the optical fiber under test 20, and amplifies the differentially processed optical signal through the amplifier 11213 and converts it into an electrical signal and outputs it to the data processing module 1122. The data processing module 1122 determines the temperature and stress distribution at various points in the optical fiber under test 20 based on the linear relationship between Brillouin frequency shift and temperature and strain.

[0098] In the above technical solution, by setting up a tight-buffered sensing fiber 1091, a loose-buffered sensing fiber 1081, and an optoelectronic differential module 1121, the variable causing the test of the sensing fiber 20 is identified, and the data processing module 1122 is used to determine the temperature and stress distribution at various points on the sensing fiber 20. This solves the problem in existing technologies where the temperature and strain measurements are inaccurate and slow due to the cross-sensitivity between temperature and strain. It enables simultaneous measurement of temperature and strain at various points on the sensing fiber and accelerates the measurement speed.

[0099] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0100] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A measurement system, characterized in that, The measurement system includes: The system comprises a first sensing fiber, a second sensing fiber, and a processing module; wherein the first sensing fiber is sensitive to temperature or strain; and the second sensing fiber is sensitive to both temperature and strain. The first and second reference beams, the first and second probe beams of the sensing fiber under test are acquired; wherein, the first and second reference beams are two beams obtained after the second coupler splits the beams, and the first and second probe beams are two beams obtained after the third coupler splits the beams. The first sensing fiber receives the first probe light and the first reference light to generate a first back-brillouin scattering light signal. The second sensing fiber receives the second probe light and the second reference light, and generates a second back-brillouin scattering light signal; The processing module determines whether the first back-blown Brillouin scattered light signal and the second back-blown Brillouin scattered light signal are consistent, and determines that the change in the sensing fiber under test is caused by temperature or strain.

2. The measurement system according to claim 1, characterized in that, The measurement system further includes: a processing module; The processing module determines whether the first backscattered Brillouin light signal and the second backscattered Brillouin light signal are consistent, and determines that the change in the sensing fiber under test is caused by temperature or strain, specifically including: When the first sensing fiber is sensitive to temperature, and the processing module detects that the first backscattered Brillouin light signal and the second backscattered Brillouin light signal are consistent, it is determined that the sensing fiber under test is affected by temperature changes. When the first sensing fiber is sensitive to temperature, and the processing module detects that the first backscattered Brillouin light signal and the second backscattered Brillouin light signal are inconsistent, it is determined that the sensing fiber under test is changed by strain. When the first sensing fiber is sensitive to strain, and the processing module detects that the first backscattered Brillouin light signal and the second backscattered Brillouin light signal are consistent, it is determined that the sensing fiber under test is changed by strain. When the first sensing fiber is sensitive to strain, and the processing module detects that the first backscattered Brillouin light signal and the second backscattered Brillouin light signal are inconsistent, it is determined that the sensing fiber under test is affected by temperature changes.

3. The measurement system according to claim 2, characterized in that, The measurement system also includes: a laser, a first coupler, an electro-optic modulation module, a filtering module, and a third coupler; Acquiring the first and second reference beams, and the first and second probe beams of the fiber optic cable under test, specifically includes: The laser emits a continuous narrow linewidth light source to the first coupler; The first coupler divides the narrow linewidth light source into a first optical signal and a second optical signal according to a first preset ratio; and inputs the first optical signal to the electro-optic modulation module; The electro-optic modulation module is used to detect the frequency shift of the optical signal and connect it to the optical fiber under test, and connect the output detection light of the optical fiber to the filtering module. The filtering module obtains a preset wavelength in the output probe light and filters out the remaining wavelengths, and outputs the output probe light to the third coupler; The third coupler divides the output probe light into a first probe light and a second probe light according to a second preset ratio, thereby obtaining the first probe light and the second probe light of the sensing fiber under test.

4. The measurement system according to claim 3, characterized in that, The measurement system further includes: a pulse modulation module and a second coupler; Acquiring the first and second reference beams, and the first and second probe beams of the optical fiber under test, specifically also includes: The second optical signal is input to the pulse modulation module, which pulse modulates the second optical signal and outputs the modulated and amplified pulsed light to the second coupler. The second coupler divides the modulated and amplified pulsed light into a first reference light and a second reference light according to a third preset ratio, thereby obtaining the reference light and the second reference light.

5. The measurement system according to claim 4, characterized in that, The measurement system further includes: a first circulator and a second circulator; The first circulator has a first port, a second port, and a third port; The first reference light is input to the first port of the first circulator and output to the first sensing fiber through the second port of the first circulator. The first probe light is input to the first sensing optical fiber; The first sensing fiber generates the first back-brillouin scattered light signal and outputs it to the processing module through the third port of the first circulator. The second circulator has a first port, a second port, and a third port; The second reference light is input to the first port of the second circulator and output to the second sensing fiber through the second port of the second circulator. The second probe light is input to the second sensing fiber; The second sensing fiber generates the second back-blown Brillouin scattering light signal and outputs it to the processing module through the third port of the second circulator.

6. The measurement system according to claim 2, characterized in that, The processing module specifically includes: an optoelectronic differential module and a data processing module; When the photoelectric differential module detects that the output information of the third port of the first circulator is consistent with the output information of the third port of the second circulator, it determines that the temperature or strain has caused a change in the optical fiber under test. When the photoelectric differential module detects that the output information of the third port of the first circulator and the output information of the third port of the second circulator are inconsistent, it determines that the strain or temperature has caused a change in the sensing fiber under test. The data processing module determines the temperature and stress distribution at various points in the optical fiber under test based on the output of the photoelectric differential module and the relationship between Brillouin frequency shift, strain, and temperature.

7. The measurement system according to claim 6, characterized in that, The photoelectric differential module specifically includes: A first avalanche photodiode, a second avalanche photodiode, and an amplifier; wherein the first avalanche photodiode and the second avalanche photodiode have opposite polarities; used for differential processing of optical signals; The first avalanche photodiode receives the first output optical signal from the third port of the first circulator; the second avalanche photodiode receives the second output optical signal from the third port of the second circulator. The amplifier receives the differentially divided first output optical signal and the second output optical signal, and amplifies the differentially divided first output optical signal and the second output optical signal.

8. The measurement system according to claim 7, characterized in that, The pulse modulation module specifically includes: an acousto-optic modulator, a first erbium-doped fiber amplifier, and a polarization scrambler; The acousto-optic modulator receives a second optical signal and modulates the second optical signal into a pulsed optical signal. The first erbium-doped fiber amplifier amplifies the power of the pulsed optical signal to obtain an amplified pulsed optical signal; The polarization scrambler is used to eliminate the impact of polarization-dependent loss on system performance and improve the stability of system signals.

9. The measurement system according to claim 8, characterized in that, The electro-optic modulation module specifically includes: Electro-optic modulator and second erbium-doped fiber amplifier; The electro-optic modulator receives a first optical signal and periodically modulates the optical frequency of the first optical signal to obtain a modulated optical signal. The second erbium-doped fiber amplifier amplifies the modulated optical signal to obtain an amplified optical signal.

10. The measurement system according to any one of claims 1 to 9, characterized in that, The first sensing fiber includes a loosely fitted sensing fiber, and the second sensing fiber includes a tightly fitted sensing fiber.

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