Brillouin gain-loss dual-mechanism optical fiber sensing monitor and control method

Abstract

The invention relates to the technical field of optical fibers, in particular to a Brillouin gain-loss dual-mechanism type optical fiber sensing monitor and a control method. According to the monitor, a laser beam emitted by a fixed wavelength laser is divided into two paths of optical signals through a polarization-maintaining coupler, one path of optical signals enters a pump pulse light path, and the other path of optical signals enters a probe light path; pump pulse light generated by the pump pulse light path and probe light generated by the probe light path respectively enter the single-mode sensing optical fiber. After the continuous probe light and the pump pulse light generate a stimulated Brillouin scattering effect in the single-mode sensing optical fiber, a generated backward Brillouin scattering signal enters the photoelectric detector to be converted into an electric signal, and the computer processes the input electric signal to complete the measurement and demodulation processes; wherein the computer controls the optical adjustable filter to output a + 1 or-1 sideband optical signal as probe light according to the selected near-end measurement mode or far-end measurement mode and the target temperature of the optical adjustable filter.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber technology, and in particular to a Brillouin gain-loss dual mechanism optical fiber sensor monitor and a control method. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Optical fiber sensing technology is widely used in the field of structural health of large infrastructure, such as submarine optical cables, roads, bridges, tunnels, aircraft, etc., due to its good performance of anti-electromagnetic interference, anti-radiation, small size and light weight. Brillouin optical time domain analysis (BOTDA) optical fiber sensing technology based on stimulated Brillouin scattering (SBS) is one of the most representative technologies in distributed optical fiber sensing technology. Compared with other optical fiber sensing solutions, it has the advantages of long sensing distance, strong signal and high accuracy.

[0004] Traditional BOTDA sensing measurement schemes include gain-type BOTDA and loss-type BOTDA. Both schemes require pulsed pump light and single-frequency continuous detection light to be injected from both ends of the single-mode sensing fiber respectively. After SBS occurs in the fiber, the backward Brillouin scattering signal is measured to obtain the Brillouin frequency shift of the entire fiber, thereby obtaining the temperature or strain change. For the gain-type BOTDA, the pump pulse light frequency is higher than the detection light. When SBS occurs, the detection light generates gain, and the pump pulse light power is always consumed. Therefore, the sensing distance is limited and it is only suitable for near-end measurement. For the loss-type BOTDA, the pump pulse light frequency is lower than the detection light. The energy of the latter is transferred to the former, and the detection light generates loss. Since the pump pulse light is always amplified, the sensing distance can be extended, which is more suitable for far-end measurement but not for near-end measurement.

[0005] In order to solve the problem that the measurement accuracy of the near end and the far end cannot be taken into account at the same time, the following solutions are currently proposed: Method 1: Through the simultaneous emission of gain and loss pump pulses, the two pump pulse pairs gain and lose the continuous detection wave respectively, so the detection wave will obtain a net gain. However, in the pump branch, two fiber Bragg gratings (FBGs) are used to filter out the gain pulse and the loss pulse respectively. The entire experimental device requires the use of 3 EOMs and 3 FBGs, and the experimental device is highly complex. In addition, it is necessary to control the two pump pulses to enter the optical fiber at the same time, and it is necessary to ensure that the power and polarization state are equal, which makes the experiment difficult to implement.

[0006] Method 2: A double-sideband detection scheme based on Stokes and anti-Stokes differential pulse pairs. This scheme uses Stokes and anti-Stokes differential pulse pairs, and the probe wave consists of three frequency components with the same power to balance the power of the two pump pulses. This scheme needs to ensure the same pump pulse power.

[0007] Method 3: A BOTDA sensing scheme using a frequency-shift keying probe wave is proposed, which can compensate for the distortion of the pulse spectrum during long-distance detection, but the modulation method is complex.

[0008] The above three schemes all modulate the input optical signal of the optical fiber to solve the double-mechanism problem. However, there are problems such as complex modulation methods, high system costs, and it is also difficult to avoid non-local effects and pump depletion when freely switching between short-distance proximal measurements and long-distance distal high-precision measurements. Summary of the Invention

[0009] In order to solve the technical problems existing in the above background technology, the present invention provides a Brillouin gain-loss dual-mechanism optical fiber sensing monitor and control method. The present invention precisely controls the temperature of an optical tunable filter (Thermoelectric Cooler Fiber Bragg Grating, TEC-FBG) to change the ±1 sideband optical signals. When the -1 sideband optical signal is used as the probe optical signal, a Brillouin gain-type BOTDA monitor is formed, and when the +1 sideband optical signal is used as the probe optical signal, a Brillouin loss-type BOTDA monitor is formed, so as to realize the switching of the Brillouin gain-loss mechanism, and further realize high-precision measurement results at both the proximal and distal ends of the same system.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions: The first aspect of the present invention provides a Brillouin gain-loss dual-mechanism optical fiber sensing monitor.

[0011] A Brillouin gain-loss dual-mechanism optical fiber sensing monitor includes: a fixed-wavelength laser, a polarization-maintaining coupler, a pump pulse optical path, a probe optical path, a single-mode sensing optical fiber, a photodetector, and a computer. The probe optical path includes an optical tunable filter; The laser beam emitted by the fixed-wavelength laser is divided into two optical signals by the polarization-maintaining coupler. One optical signal enters the pump pulse optical path, and the other optical signal enters the probe optical path; the pump pulse light generated by the pump pulse optical path and the probe light generated by the probe optical path respectively enter the single-mode sensing optical fiber; After the continuous probe light and the pump pulse light generate the stimulated Brillouin scattering effect in the single-mode sensing optical fiber, the generated backward Brillouin scattering signal enters the photodetector and is converted into an electrical signal. The computer processes the input electrical signal to complete the measurement and demodulation process; Among them, according to the selected proximal measurement mode or distal measurement mode, the computer calculates the target temperature of the optical tunable filter based on the current temperature of the optical tunable filter, the central wavelength of the optical tunable filter corresponding to the current temperature, and the central wavelength of the fixed laser; according to the target temperature of the optical tunable filter, the computer controls the optical tunable filter to output a +1 or -1 sideband optical signal as the probe light.

[0012] Further, the pump pulse optical path includes: a semiconductor optical amplifier, a random polarization scrambler, an erbium-doped fiber amplifier, and a first single-mode circulator. The optical signal entering the pump pulse optical path passes through the semiconductor optical amplifier to generate a pulsed light; the pulsed light sequentially passes through the random polarization scrambler and the erbium-doped fiber amplifier to generate a pump pulse light, and the pump pulse light enters the first port of the first single-mode circulator and is output from the second port of the first single-mode circulator, and then enters the single-mode sensing optical fiber.

[0013] Further, the semiconductor optical amplifier is driven by a pulse signal sent by an acquisition card.

[0014] Further, the acquisition card is used to set the sampling rate, sampling length, and frequency of the trigger signal, receive the electrical signal, and upload it to the computer.

[0015] Further, the probe light optical path includes: an electro-optic modulator, a second single-mode circulator, and an optical isolator. The optical signal entering the probe light optical path passes through the electro-optic modulator to generate ±1 sideband optical signals, and the ±1 sideband optical signals enter the first port of the second single-mode circulator, enter the optical tunable filter through the second port of the second single-mode circulator, select a +1 or -1 sideband optical signal and output it from the third port of the second single-mode circulator, and then enter the single-mode sensing optical fiber through the optical isolator.

[0016] Further, the electro-optic modulator is driven by a sweepable microwave signal from a microwave source module.

[0017] Further, the polarization-maintaining coupler is used to divide the laser beam into two optical signals with an optical power ratio of 10:90.

[0018] Further, if the proximal measurement mode is selected, the target temperature of the optical tunable filter is:

[0019]

[0020] Among them, represents the central wavelength of the optically tunable filter under represents the central wavelength of the fixed laser, represents the central wavelength of the optically tunable filter under T0, where T0 represents the current temperature of the optically tunable filter, and x represents the wavelength parameter.

[0021] Further, if the remote measurement mode is selected, the target temperature of the optically tunable filter is:

[0022]

[0023] wherein, represents the central wavelength of the optically tunable filter under represents the central wavelength of the fixed laser, represents the central wavelength of the optically tunable filter under T0, where T0 represents the current temperature of the optically tunable filter, and x represents the wavelength parameter.

[0024] The second aspect of the present invention provides a control method for a Brillouin gain-loss dual-mechanism fiber optic sensing monitor.

[0025] A control method for a Brillouin gain-loss dual-mechanism fiber optic sensing monitor according to the first aspect, comprising: selecting a measurement mode; If it is the proximal measurement mode, calculate the central wavelength of the optically tunable filter corresponding to the target temperature of the optically tunable filter according to the sum of the central wavelength of the fixed laser and the wavelength parameter; calculate the target temperature of the optically tunable filter according to the central wavelength of the optically tunable filter corresponding to the target temperature of the optically tunable filter, the current temperature of the optically tunable filter, and the central wavelength of the optically tunable filter corresponding to the current temperature, so that the optically tunable filter outputs a -1 sideband optical signal as the probe light; If it is the remote measurement mode, calculate the central wavelength of the optically tunable filter corresponding to the target temperature of the optically tunable filter according to the difference between the central wavelength of the fixed laser and the wavelength parameter; calculate the target temperature of the optically tunable filter according to the central wavelength of the optically tunable filter corresponding to the target temperature of the optically tunable filter, the current temperature of the optically tunable filter, and the central wavelength of the optically tunable filter corresponding to the current temperature, so that the optically tunable filter outputs a +1 sideband optical signal as the probe light.

[0026] Compared with the prior art, the beneficial effects of the present invention are: The present invention provides a Brillouin gain-loss dual-mechanism fiber optic sensing monitor and control method. The laser beam emitted by a fixed-wavelength laser is divided into two optical signals by a polarization-maintaining coupler. One optical signal enters the pump pulse optical path, and the other enters the probe optical path. The pump pulse light generated by the pump pulse optical path and the probe light generated by the probe optical path respectively enter a single-mode sensing fiber. After the continuous probe light and the pump pulse light undergo the stimulated Brillouin scattering effect in the single-mode sensing fiber, the generated backward Brillouin scattering signal enters a photodetector and is converted into an electrical signal. The computer processes the input electrical signal to complete the measurement and demodulation process. The computer calculates the target temperature of the optical tunable filter based on the current temperature of the optical tunable filter, the central wavelength of the optical tunable filter corresponding to the current temperature, and the central wavelength of the fixed laser according to the selected proximal measurement mode or distal measurement mode. According to the target temperature of the optical tunable filter, the optical tunable filter is controlled to output a +1 or -1 sideband optical signal as the probe light. The present invention obtains the Brillouin gain spectrum or loss spectrum by controlling the optical tunable filter, thereby leveraging the advantages of each mechanism to achieve high-precision measurement results at both the proximal and distal ends of the same system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0028] Figure 1 is a schematic structural diagram of a Brillouin gain-loss dual-mechanism fiber optic sensing monitor shown in an embodiment of the present invention; Figure 2 is a schematic diagram of the control principle of a TEC-FBG tunable filter shown in an embodiment of the present invention; FIG. 3(a) is a waveform diagram of pump pulse optical signals with different pulse widths incident on a single-mode sensing fiber shown in an embodiment of the present invention; FIG. 3(b) is a waveform diagram of the probe light double-sideband signal and two single-sideband signals shown in an embodiment of the present invention; Figure 4 is a flowchart of a Brillouin gain-loss dual-mechanism distributed fiber optic sensing monitoring method shown in an embodiment of the present invention; Wherein, 1. Fixed-wavelength laser, 2. Polarization-maintaining coupler, 3. Semiconductor optical amplifier, 4. Random polarization scrambler, 5. Erbium-doped fiber amplifier, 6. First single-mode circulator, 7. Single-mode sensing fiber, 8. Electro-optic modulator, 9. Microwave source module, 10. Second single-mode circulator, 11. Optical tunable filter, 12. Optical isolator, 13. Photodetector, 14. Acquisition card, 15. Computer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0030] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which the present invention belongs.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] It should be noted that the flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of methods and systems according to various embodiments of the present disclosure. It should be noted that each block in the flowchart or block diagram may represent a module, a program segment, or a part of code, and the module, program segment, or part of code may include one or more executable instructions for implementing the logical functions specified in each embodiment. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than marked in the accompanying drawings. For example, two consecutive blocks shown may actually be executed substantially in parallel, or they may sometimes be executed in the reverse order, depending on the functions involved. Similarly, it should be noted that each block in the flowchart and / or block diagram, and the combinations of blocks in the flowchart and / or block diagram, may be implemented using a dedicated hardware-based system for performing the specified functions or operations, or may be implemented using a combination of dedicated hardware and computer instructions.

[0033] Embodiment 1 As Figure 1 shown, this embodiment provides a Brillouin gain-loss dual-mechanism fiber optic sensing monitor, including: a fixed-wavelength laser 1, a polarization-maintaining coupler 2, a pump pulse light optical path, a probe light optical path, a single-mode sensing fiber 7, a photodetector 13, and a computer 15; The fixed-wavelength laser 1 outputs a continuous laser beam with a fixed central wavelength, which is divided into two optical branches, namely the pump pulse light optical path and the probe light optical path, through a 10:90 polarization-maintaining coupler 2.

[0034] Specifically, the optical path of the pump pulse light is as follows: 10% of the optical signal output by the polarization-maintaining coupler 2 first passes through the semiconductor optical amplifier 3. The pulse signal sent by the acquisition card 14 drives the semiconductor optical amplifier 3 to modulate the continuous light to generate a pulse optical signal. Subsequently, the pulse light passes through the random polarization scrambler 4 to randomly and uniformly perturb the polarization state of the light beam, and then enters the erbium-doped fiber amplifier 5 for optical power amplification to form the pump pulse light required by the system. Then, the pulse light generated by the erbium-doped fiber amplifier 5 enters through port 1 of the first single-mode circulator 6 and enters the single-mode sensing fiber 7 through port 2.

[0035] Specifically, the optical path of the probe light is as follows: 90% of the optical signal output by the polarization-maintaining coupler 2 first enters the electro-optic modulator 8. The microwave source module 9 outputs a sweepable microwave signal of 8 - 12 GHz to drive the electro-optic modulator 8 to generate carrier-suppressed first-order upper and lower sidebands. The double sidebands enter through port 1 of the second single-mode circulator 10 and enter the TEC-FBG optical tunable filter 11 through port 2 of the second single-mode circulator 10 for filtering. According to the actual sensing distance requirement, by controlling the TEC-FBG optical tunable filter 11, the +1 or -1 sideband optical signal is selected as the probe light and output from the third port of the second single-mode circulator, and then enters the single-mode sensing fiber 7 through the optical isolator 12.

[0036] After the continuous probe light and the pump pulse light undergo the stimulated Brillouin scattering effect SBS in the single-mode sensing fiber 7, the backward Brillouin scattering signal is emitted from port 3 of the first single-mode circulator 6, and the backward Brillouin scattering signal is converted into an electrical signal by the photodetector 13, received by the high-speed acquisition card 14, and finally input into the computer 15 for data processing, thus completing the entire measurement and demodulation process.

[0037] In some embodiments, the fixed wavelength of the fixed wavelength laser 1 is 1550 nm, the power is 20 mW, the narrow linewidth is 3 kHz, and the pigtail is a polarization-maintaining fiber.

[0038] In some embodiments, the polarization-maintaining coupler 2 is used to divide the optical signal into two optical signals with an optical power ratio of 10:90.

[0039] In some embodiments, the semiconductor optical amplifier 3 is used to set the width of the pulse light.

[0040] In some embodiments, the random polarization scrambler 4 is used to randomly and uniformly disrupt the polarization state of the light wave to eliminate the influence of polarization noise by averaging.

[0041] In some embodiments, the erbium-doped fiber amplifier 5 is used to amplify the power of the pulse optical signal.

[0042] In some embodiments, the first single-mode circulator 6 and the second single-mode circulator 10 are configured to restrict the optical signal to be transmitted only in the unidirectional direction of the ring.

[0043] In some embodiments, the electro-optic modulator 8 is configured to perform carrier-suppressed double-sideband modulation.

[0044] In some embodiments, the microwave source module is configured to set and generate a microwave modulation signal with a frequency of 8 - 12 GHz and a power up to 23 dB.

[0045] In some embodiments, the TEC-FBG optical tunable filter 11 is configured to change the passband and center wavelength of the FBG by controlling the temperature of the TEC.

[0046] In some embodiments, the optical isolator 12 is configured to restrict the optical signal to be transmitted only unidirectionally.

[0047] In some embodiments, the photodetector 13 is configured to convert the optical signal into an electrical signal.

[0048] In some embodiments, the acquisition card 14 is configured to set the sampling rate, sampling length, frequency of the trigger signal, and acquire the electrical signal.

[0049] In some possible implementation manners, according to the wavelength output by the fixed-wavelength laser 1, the computer 15 precisely controls the temperature of the TEC-FBG optical tunable filter 11, thereby changing its passband range, and only using the ±1 sidebands can realize the free switching between the Brillouin gain mechanism and the loss mechanism. The specific control principle is as Figure 2 shown. When the temperature is set to T1, the TEC-FBG optical tunable filter 11 uses the -1 sideband optical signal output by the electro-optic modulator 8 as the probe optical signal to form a Brillouin gain type BOTDA monitor, and the system detects the Brillouin gain spectrum (BGS) for short-distance proximal measurement; when the temperature is set to T2, the TEC-FBG optical tunable filter 11 uses the +1 sideband output by the electro-optic modulator 8 as the probe optical signal, as a Brillouin loss type BOTDA monitor, and the system detects the Brillouin loss spectrum (BLS) for long-distance distal measurement. Among them, the temperatures set by T1 and T2 are determined by the center wavelength of the fixed-wavelength laser 1.

[0050] Among them, T1 is calculated using the following formula:

[0051]

[0052] Among them, represents the center wavelength of the optical tunable filter under represents the central wavelength of the fixed laser, represents the central wavelength of the optically tunable filter at T0, where T0 represents the current temperature of the optically tunable filter, and x represents the wavelength parameter.

[0053] wherein, T2 is calculated by the following formula:

[0054]

[0055] wherein, represents the central wavelength of the optically tunable filter at represents the central wavelength of the fixed laser, represents the central wavelength of the optically tunable filter at T0, where T0 represents the current temperature of the optically tunable filter, and x represents the wavelength parameter.

[0056] Through the above solution, the present invention can give full play to the advantages of each mechanism, respectively achieve high-precision measurement for short-distance proximal and long-distance distal, and further improve the system stability and reduce the cost.

[0057] Embodiment 2 The object of the present invention is to provide a control method for a Brillouin gain-loss dual-mechanism fiber optic sensing monitor aiming at the problems of the distributed fiber optic sensing monitor based on the BOTDA principle, such as the inability to balance the measurement accuracy at the proximal and distal ends, poor stability, and high cost.

[0058] The control method described in the present invention needs to be applied to a Brillouin gain-loss dual-mechanism fiber optic sensing monitor, as Figure 1 shown, the monitor includes: a fixed-wavelength laser 1, a polarization-maintaining coupler 2, a semiconductor optical amplifier 3, a random polarization scrambler 4, an erbium-doped fiber amplifier 5, a first single-mode circulator 6, a single-mode sensing fiber 7, an electro-optic modulator 8, a microwave source module 9, a second single-mode circulator 10, an optically tunable filter 11, an optical isolator 12, a photodetector 13, an acquisition card 14, and a computer 15.

[0059] Specifically, the fixed-wavelength laser 1 emits an optical signal to the polarization-maintaining coupler 2, and the polarization-maintaining coupler 2 has two output paths. Among them, the signal path of the pump pulse optical path is that 10% of the continuous light output from the polarization-maintaining coupler 2 sequentially enters the semiconductor optical amplifier 3, the random polarization scrambler 4, the erbium-doped fiber amplifier 5, and is input from the first port of the first single-mode circulator 6, and is output from the second port and injected into the single-mode sensing fiber 7. Fig. 3(a) shows the pump pulse signals with different pulse widths injected into the single-mode sensing fiber. In addition, for the continuous detection optical path, 90% of the continuous light output from the polarization-maintaining coupler 2 first enters the electro-optic modulator 8, and the output is the double-sideband signal shown in Fig. 3(b). After being input from the first port of the second single-mode circulator, it enters the TEC-FBG optical tunable filter 11 through the second port to select one of the single-sideband signals. The upper sideband or the lower sideband signal shown in Fig. 3(b) after filtering is output from the third port of the second single-mode circulator 11, and then is injected into the single-mode sensing fiber 7 through the optical isolator 12. Finally, the output from the third port of the first single-mode circulator 6 sequentially enters the photodetector 13, the acquisition card 14, and the computer 15.

[0060] The Brillouin gain-loss dual-mechanism fiber sensing monitor can achieve high-precision measurement of the proximal or distal end of the single-mode sensing fiber 7 for different application scenarios.

[0061] The control method, As Figure 4 shown, after the system starts, select the measurement mode, the proximal measurement or the distal measurement mode.

[0062] During proximal measurement, by controlling the temperature adjust the central wavelength λ of the TEC-FBG optical tunable filter 11 -1 to be near the central wavelength of the fixed laser λ + 0.088 nm (corresponding to the fiber Brillouin frequency shift of 11 GHz). If the current temperature of the TEC-FBG optical tunable filter 11 is T0 (°C), and the central wavelength at T0 is λ0 (nm), then . Among them, , represents the central wavelength of the optical tunable filter at represents the central wavelength of the fixed laser, represents the central wavelength of the optical tunable filter at T0, and x represent the wavelength parameters, k = 0.01 nm, x = . Through the computer 15, the calculated temperature Send it to the TEC-FBG optical tunable filter 11. At this time, the lower sideband of the detected optical double-sideband signal in Fig. 3(b) is filtered out, forming a Brillouin gain mechanism type BOTDA detector, realizing high-precision sensing measurement at the proximal end of the single-mode sensing optical fiber 7. At this time, collect the Brillouin scattering signal and judge the measurement effect. If the effect is good, exit the process. If the effect is poor, switch to the remote mode.

[0063] When measuring at the remote end, by controlling the temperature, adjust the central wavelength λ +1 (nm) of the TEC-FBG optical tunable filter 11 to the fixed laser wavelength λ - 0.088 (nm), and calculate the temperature through the computer 15 , . Among them, , represents the central wavelength of the optical tunable filter under represents the central wavelength of the fixed laser, represents the central wavelength of the optical tunable filter under T0, and x represent wavelength parameters, k = 0.01nm, x = . The computer 15 will send the calculated to the TEC-FBG optical tunable filter 11. At this time, the upper sideband of the detected optical double-sideband signal in Fig. 3(b) is filtered out, forming a Brillouin loss mechanism type BOTDA detector, realizing high-precision sensing measurement at the remote end of the single-mode sensing optical fiber 7. Therefore, by this method of controlling the TEC-FBG, the Brillouin gain mechanism and the loss mechanism are freely switched, and high-precision measurement at the proximal or remote end is realized for different application scenarios.

[0064] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Brillouin gain-loss dual-mechanism fiber optic sensing monitor, characterized in that Including: A fixed-wavelength laser, a polarization-maintaining coupler, a pump pulse light optical path, a probe light optical path, a single-mode sensing optical fiber, a photodetector, and a computer. The probe light optical path includes an optically tunable filter; The laser beam emitted by the fixed-wavelength laser is split into two optical signals by the polarization-maintaining coupler. One optical signal enters the pump pulse light optical path, and the other optical signal enters the probe light optical path; The pump pulse light generated by the pump pulse light optical path and the probe light generated by the probe light optical path respectively enter the single-mode sensing optical fiber; After the continuous probe light and the pump pulse light undergo the stimulated Brillouin scattering effect in the single-mode sensing optical fiber, the generated backward Brillouin scattering signal enters the photodetector and is converted into an electrical signal, and the computer processes the input electrical signal to complete the measurement and demodulation process; Among them, the computer calculates the target temperature of the optically tunable filter based on the selected proximal measurement mode or distal measurement mode, the current temperature of the optically tunable filter, the central wavelength of the optically tunable filter corresponding to the current temperature, and the central wavelength of the fixed laser; According to the target temperature of the optically tunable filter, control the optically tunable filter to output a +1 or -1 sideband optical signal as the probe light.

2. The Brillouin gain-loss dual-mechanism fiber optic sensing monitor according to claim 1, wherein The pump pulse light optical path includes: a semiconductor optical amplifier, a random polarization scrambler, an erbium-doped fiber amplifier, and a first single-mode circulator. The optical signal entering the pump pulse light optical path passes through the semiconductor optical amplifier to generate pulsed light; The pulsed light sequentially passes through the random polarization scrambler and the erbium-doped fiber amplifier to generate pump pulse light, and the pump pulse light enters the first port of the first single-mode circulator and is output from the second port of the first single-mode circulator, and then enters the single-mode sensing optical fiber.

3. The Brillouin gain-loss dual-mechanism fiber optic sensing monitor according to claim 2, characterized in that, The semiconductor optical amplifier is driven by a pulse signal sent by an acquisition card.

4. The Brillouin gain-loss dual-mechanism fiber optic sensing monitor according to claim 3, characterized in that, The acquisition card is used to set the sampling rate, sampling length, and frequency of the trigger signal, receive the electrical signal, and upload it to the computer.

5. The Brillouin gain-loss dual-mechanism fiber optic sensing monitor according to claim 1, characterized in that The probe light optical path includes: an electro-optic modulator, a second single-mode circulator, and an optical isolator. The optical signal entering the probe light optical path passes through the electro-optic modulator to generate ±1 sideband optical signals. The ±1 sideband optical signals enter the first port of the second single-mode circulator, enter the optically tunable filter through the second port of the second single-mode circulator, select a +1 or -1 sideband optical signal and output it from the third port of the second single-mode circulator, and then enter the single-mode sensing optical fiber through the optical isolator.

6. The Brillouin gain-loss dual-mechanism fiber optic sensing monitor according to claim 5, characterized in that, The electro-optic modulator is driven by a sweepable microwave signal from a microwave source module.

7. The Brillouin gain-loss dual-mechanism fiber optic sensing monitor according to claim 1, characterized in that, The polarization-maintaining coupler is used to divide the laser beam into two optical signals with a power ratio of 10:

90.

8. The Brillouin gain-loss dual-mechanism fiber optic sensing monitor according to claim 1, characterized in that, If the proximal measurement mode is selected, the target temperature of the optical tunable filter is as follows: Among them, represents the central wavelength of the optical tunable filter under represents the central wavelength of the fixed laser, represents the central wavelength of the optical tunable filter under T0, where T0 represents the current temperature of the optical tunable filter, and x represents the wavelength parameter.

9. The Brillouin gain-loss dual-mechanism fiber optic sensing monitor according to claim 1, characterized in that, If the remote measurement mode is selected, the target temperature of the optical tunable filter is: Among them, denotes the central wavelength of the optical tunable filter under denotes the central wavelength of the fixed laser, denotes the central wavelength of the optical tunable filter under T0, where T0 represents the current temperature of the optical tunable filter, and x represents the wavelength parameter.

10. A control method for a Brillouin gain-loss dual-mechanism fiber sensing monitor according to any one of claims 1-9, including: Select a measurement mode; If it is in the proximal measurement mode, calculate the central wavelength of the optical tunable filter corresponding to the target temperature of the optical tunable filter according to the sum of the central wavelength of the fixed laser and the wavelength parameter; calculate the target temperature of the optical tunable filter according to the central wavelength of the optical tunable filter corresponding to the target temperature of the optical tunable filter, the current temperature of the optical tunable filter, and the central wavelength of the optical tunable filter corresponding to the current temperature, so that the optical tunable filter outputs a -1 sideband optical signal as the detection light; If it is in the distal measurement mode, calculate the central wavelength of the optical tunable filter corresponding to the target temperature of the optical tunable filter according to the difference between the central wavelength of the fixed laser and the wavelength parameter; calculate the target temperature of the optical tunable filter according to the central wavelength of the optical tunable filter corresponding to the target temperature of the optical tunable filter, the current temperature of the optical tunable filter, and the central wavelength of the optical tunable filter corresponding to the current temperature, so that the optical tunable filter outputs a +1 sideband optical signal as the detection light.

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