SF6 decomposition product monitoring optical fiber photoacoustic gas sensor, system and method

Abstract

The invention discloses an SF6 decomposition product monitoring optical fiber photoacoustic gas sensor, system and method, belongs to the technical field of optical fiber sensing and measurement of power transmission and transformation equipment operation and maintenance, and solves the problem of high airflow noise generally existing in an existing SF6 decomposition product gas detection scheme. The photoacoustic signals in the two photoacoustic resonance tubes are the same in amplitude and opposite in phase, and the incoherent noise in the tubes is the same in amplitude and phase; the two cantilever beam sensors for detecting photoacoustic signals and the two photoacoustic resonance tubes which are mounted in the cantilever beam sensor mounting holes form a differential double-tube photoacoustic cell structure, so that the influence caused by airflow noise can be inhibited; the designed flow guide pipe is beneficial to dispersing the flow of the SF6 gas flowing in and out of the photoacoustic resonance pipe, so that the flow of the SF6 gas flowing in and out of the photoacoustic resonance pipe is smoother, noise caused by too large flow is avoided, and meanwhile flow noise generated by turbulent flow and vortex in the gas flowing process is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of optical fiber sensing and measurement technology in the field of power transmission and transformation equipment operation and maintenance, and relates to a SF 6 Fiber optic photoacoustic gas sensor, system and method for decomposition product monitoring. Background Art

[0002] Sulfur hexafluoride gas (SF 6 ) has stable chemical properties and excellent insulation, which makes it an ideal insulating and arc-extinguishing medium and is widely used in the field of gas-insulated equipment. When there are impurities or traces of water and oxygen in gas-insulated equipment, sulfur hexafluoride gas will decompose into various toxic or corrosive gases during operation through faults such as partial discharge or local overheating. By detecting H 2 S. SO 2 The decomposition products of sulfur hexafluoride such as , CO, and HF can timely detect the decline of the insulation performance inside the equipment, so as to take corresponding measures for maintenance and avoid accidents. Therefore, in order to ensure the long-term, reliable and trouble-free operation of gas-insulated equipment, the insulation status of the equipment must be monitored online in real time.

[0003] Photoacoustic spectroscopy has become the mainstream of gas detection technology, with the advantages of good sensitivity, selectivity, no background and fast response. The target gas molecules absorb laser light of a specific wavelength, transition from a low energy state to a high energy state, and return to a low energy state through a non-radiative transition. This process is accompanied by the release of heat. By modulating the excitation light source at a certain frequency, the gas molecules will periodically release the absorbed light energy through heat, causing periodic thermal expansion of the gas and generating sound waves. Traditional electrical acoustic wave sensors have too much noise, while optical fiber acoustic wave sensors are immune to electromagnetic interference. Therefore, optical fiber acoustic wave sensors can be used to pick up acoustic wave information and convert it into optical signals. The gas concentration information can be obtained from the optical signals through a demodulation system. Literature Detection of SF 6 Gas decomposition component H 2 A high-sensitivity fiber-optic Fabry-Perot (FP) photoacoustic gas detection system with anti-electromagnetic interference and intrinsic safety characteristics is proposed for quantitative analysis of sulfur hexafluoride decomposition components H 2 However, sulfur hexafluoride has special physical properties, which is mainly reflected in its high gas density, resulting in excessive gas flow noise, making it impossible to monitor the decomposition products of sulfur hexafluoride online in real time. Summary of the invention

[0004] The technical solution of the present invention is used to solve the problem of large airflow noise that is common in the prior art gas detection solutions for sulfur hexafluoride decomposition products.

[0005] The present invention solves the above technical problems through the following technical solutions: The present invention provides a SF 6 The decomposition product monitoring optical fiber photoacoustic gas sensor comprises: an air inlet buffer chamber, a differential double-tube photoacoustic pool structure, and an air outlet buffer chamber; the open end of the air inlet buffer chamber is sealed and connected to one side of the differential double-tube photoacoustic pool structure, and the other side of the differential double-tube photoacoustic pool structure is sealed and connected to the open end of the air outlet buffer chamber; an excitation light source optical fiber collimator mounting hole is provided at one end of the air inlet cavity of the air inlet buffer chamber, and the other end of the air inlet cavity is open, and an air inlet hole processed on one side of the air inlet buffer chamber is connected to the air inlet cavity; the differential Two identical first photoacoustic resonance tubes, a second photoacoustic resonance tube, and a plurality of guide tubes are processed in the double-tube photoacoustic pool structure; two cantilever beam sensor mounting holes are symmetrically processed at the center positions on both sides of the differential double-tube photoacoustic pool structure for installing cantilever beam sensors, and the cantilever beam sensors are respectively corresponding to the outer walls of the first photoacoustic resonance tube and the second photoacoustic resonance tube; one end of the air outlet cavity of the air outlet buffer chamber is closed, and the other end of the air outlet cavity is open, and the air outlet hole processed on one side of the air outlet buffer chamber is connected to the air outlet cavity.

[0006] Preferably, the diameter of the flow guide tube is larger than the diameter of the first photoacoustic resonance tube or the second photoacoustic resonance tube.

[0007] Preferably, the first photoacoustic resonance tube and the second photoacoustic resonance tube are arranged bilaterally symmetrically with respect to the xoz plane.

[0008] Furthermore, the SF of the present invention 6 The decomposition product monitoring optical fiber photoacoustic gas sensor further comprises: an optical fiber collimator, which is installed in the excitation light source optical fiber collimator installation hole.

[0009] Furthermore, the SF of the present invention 6 The decomposition product monitoring optical fiber photoacoustic gas sensor also includes: two single-mode optical fibers, which are respectively connected to the cantilever beam sensors installed in the first cantilever beam sensor installation hole and the second cantilever beam sensor installation hole.

[0010] The present invention also provides a method for applying the above SF 6 A method for monitoring decomposition products using an optical fiber photoacoustic gas sensor comprises the following steps: 1) SF 6 The decomposition product enters the gas cavity from the air inlet, flows into the gas outlet cavity through the first photoacoustic resonance tube, the second photoacoustic resonance tube and the guide tube in the differential double-tube photoacoustic cell structure, and then flows out through the air outlet; 2) The excitation light is incident into the air inlet cavity through the fiber collimator, and the excitation light excites the SF in the air inlet cavity. 6 The decomposition product gas molecules propagate in the first photoacoustic resonance tube and the second photoacoustic resonance tube to form photoacoustic pressure waves, and the photoacoustic pressure waves cause the cantilever beam of the cantilever beam sensor to vibrate; 3) The detection light is input from two single-mode optical fibers. The end faces of the two single-mode optical fibers and the cantilever beam of the cantilever beam sensor form a Fabry-Perot cavity. The reflected light from the end faces of the single-mode optical fibers interferes with the reflected light from the cantilever beam. The interference spectrum is demodulated by an instrument to detect the SF. 6 Concentration of decomposition products.

[0011] The present invention also provides a SF 6 The decomposition product monitoring optical fiber photoacoustic gas sensor system comprises: a detection light source, an optical fiber coupler, an excitation light source, a high-speed spectrometer, a signal processing circuit, and a computer; the excitation light source is connected to the optical fiber photoacoustic gas sensor through an optical fiber collimator, the detection light source is connected to the optical fiber coupler through an optical fiber, the optical fiber coupler uses two single-mode optical fibers to be respectively connected to the optical fiber photoacoustic gas sensor, the output end of the optical fiber coupler is connected to the input end of the high-speed spectrometer, the output end of the high-speed spectrometer is connected to the input end of the signal processing circuit, and the output end of the signal processing circuit is connected to the input end of the computer.

[0012] Furthermore, the working process is as follows: the excitation light emitted by the excitation light source is incident on the fiber optic photoacoustic gas sensor to excite the gas molecules to be measured, the detection light emitted by the detection light source passes through the fiber optic coupler, and then enters the fiber optic photoacoustic gas sensor through two single-mode optical fibers for differential detection, the detected differential interference spectrum signal is transmitted to the high-speed spectrometer through the fiber optic coupler, the differential interference spectrum signal is processed by the signal processing circuit, and the processing result is displayed on the computer.

[0013] Preferably, the wavelength range of the high-speed spectrometer is 1525nm-1570nm, and the sampling frame rate is greater than 10kHz.

[0014] Preferably, the detection light source is a broadband detection light source.

[0015] The advantages of the present invention are: The optical fiber photoacoustic gas sensor of the present invention is designed with two identical photoacoustic resonance tubes, the photoacoustic signal amplitudes in the two photoacoustic resonance tubes are the same and the phases are opposite, while the amplitude and phase of the incoherent noise in the tubes are the same; the two cantilever beam sensors for detecting photoacoustic signals installed in the cantilever beam sensor installation hole and the first photoacoustic resonance tube and the second photoacoustic resonance tube constitute a differential double-tube photoacoustic pool structure, which is conducive to suppressing the influence of airflow noise; the designed flow guide tube is helpful to disperse the SF flowing into and out of the first photoacoustic resonance tube and the second photoacoustic resonance tube.6 The gas flow rate is such that the SF flowing into and out of the first photoacoustic resonance tube and the second photoacoustic resonance tube 6 The gas flow is smoother, avoiding the noise caused by excessive flow, and also reducing the flow noise caused by turbulence and vortexes during the gas flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the SF of the first embodiment of the present invention 6 3D perspective view of fiber optic photoacoustic gas sensor for decomposition product monitoring; Figure 2 is the SF of the first embodiment of the present invention 6 Front perspective view of the fiber optic photoacoustic gas sensor for decomposition product monitoring; Figure 3 is the SF of the first embodiment of the present invention 6 Rear perspective view of a fiber optic photoacoustic gas sensor for monitoring decomposition products; Figure 4 is the SF of the first embodiment of the present invention 6 Left perspective view of the fiber optic photoacoustic gas sensor for decomposition product monitoring; Figure 5 is the SF of the first embodiment of the present invention 6 Right perspective view of the fiber optic photoacoustic gas sensor for decomposition product monitoring; Figure 6 is the SF of the first embodiment of the present invention 6 A perspective view of a fiber optic photoacoustic gas sensor for monitoring decomposition products; Figure 7 is the SF of the first embodiment of the present invention 6 A cross-sectional oblique perspective view of a fiber optic photoacoustic gas sensor for monitoring decomposition products along the xoy plane; Figure 8 is the SF of the first embodiment of the present invention 6 A front perspective view of a cross-section taken along the xoy plane of a fiber optic photoacoustic gas sensor for monitoring decomposition products; Fig. 9 is the SF of the first embodiment of the present invention 6 A cross-sectional oblique perspective view of a fiber optic photoacoustic gas sensor for monitoring decomposition products along a vertical section along the yoz plane; Fig.10 is the SF of the first embodiment of the present invention 6 A front perspective view of a fiber optic photoacoustic gas sensor for monitoring decomposition products, taken along the yoz plane; Fig.11 SF of Embodiment 1 of the present invention 6 Decomposition product monitoring fiber photoacoustic gas sensor is different from traditional fiber photoacoustic gas sensor in measuring SF 6Noise comparison chart when decomposing product flow noise; Fig.12 is the SF of the second embodiment of the present invention 6 Block diagram of the fiber optic photoacoustic gas sensing system for decomposition product monitoring. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments: Embodiment 1 like Figures 1 to 10 As shown, the SF of the embodiment of the present invention 6 The decomposition product monitoring optical fiber photoacoustic gas sensor includes: an air inlet buffer chamber 41, a differential double-tube photoacoustic pool structure 42, and an air outlet buffer chamber 43; the open end of the air inlet buffer chamber 41 is sealedly connected to one side of the differential double-tube photoacoustic pool structure 42, and the other side of the differential double-tube photoacoustic pool structure 42 is sealedly connected to the open end of the air outlet buffer chamber 43.

[0019] The air intake buffer chamber 41 is a rectangular structure, and a cylindrical air intake cavity 411 is processed inside it along the x-axis centerline direction of the rectangular body. An excitation light source fiber collimator mounting hole 44 is opened at one end of the air intake cavity 411, and the other end of the air intake cavity 411 is open. The excitation light source fiber collimator mounting hole 44 is used to install the fiber collimator. The excitation light emitted by the excitation light source is incident into the air intake cavity 411 through the fiber collimator. An air intake hole 45 is processed on one side of the air intake buffer chamber 41, and the air intake hole 45 is connected to the air intake cavity 411.

[0020] The differential double-tube photoacoustic pool structure 42 is a rectangular parallelepiped structure, and a first photoacoustic resonance tube 421, a second photoacoustic resonance tube 422, a first flow guide tube 423, and a second flow guide tube 424 are processed along the x-axis direction of the rectangular parallelepiped. The first photoacoustic resonance tube 421, the second photoacoustic resonance tube 422, the first flow guide tube 423, and the second flow guide tube 424 are parallel, wherein the first photoacoustic resonance tube 421 and the second photoacoustic resonance tube 422 are symmetrical about the xoz plane, and the first flow guide tube 423 and the second flow guide tube 424 are symmetrical about the xoz plane. The oy plane is symmetrical up and down; the structural dimensions of the first photoacoustic resonance tube 421 and the second photoacoustic resonance tube 422 are exactly the same, and the structural dimensions of the first flow guide tube 423 and the second flow guide tube 424 are exactly the same; the diameters of the first flow guide tube 423 and the second flow guide tube 424 are larger than the diameters of the first photoacoustic resonance tube 421 and the second photoacoustic resonance tube 422, and preferably, the diameters of the first flow guide tube 423 and the second flow guide tube 424 are twice the diameters of the first photoacoustic resonance tube 421 and the second photoacoustic resonance tube 422.

[0021] The first cantilever beam sensor mounting hole 47 and the second cantilever beam sensor mounting hole 48 are symmetrically processed at the center positions on both sides of the differential double-tube photoacoustic pool structure 42. The first cantilever beam sensor mounting hole 47 and the second cantilever beam sensor mounting hole 48 are both used to install cantilever beam sensors, and the cantilever beams of the cantilever beam sensors are respectively corresponding to the outer walls of the first photoacoustic resonance tube 421 and the second photoacoustic resonance tube 422.

[0022] The air outlet buffer chamber 43 is a rectangular structure, and a cylindrical air outlet cavity 431 is processed inside it along the x-axis centerline direction of the rectangular structure. One end of the air outlet cavity 431 is closed, and the other end of the air outlet cavity 431 is open. An air outlet hole 46 is processed on one side of the air outlet buffer chamber 43, and the air outlet hole 46 is connected to the air outlet cavity 431.

[0023] SF of the embodiment of the present invention 6 The detection process of the decomposition product monitoring photoacoustic gas sensor is as follows: An optical fiber collimator is installed in the excitation light source optical fiber collimator installation hole 44, and two single-mode optical fibers are used to connect the cantilever beam sensors installed in the first cantilever beam sensor installation hole 47 and the second cantilever beam sensor installation hole 48 respectively; SF 6 The decomposition product enters the gas cavity 411 from the gas inlet 45, flows into the gas outlet cavity 431 through the first photoacoustic resonance tube 421, the second photoacoustic resonance tube 422, the first flow guide tube 423, and the second flow guide tube 424 in the differential double-tube photoacoustic cell structure 42, and then flows out through the gas outlet 46; The excitation light is incident into the air inlet cavity 411 through the optical fiber collimator, and the excitation light excites SF in the air inlet cavity 411. 6The decomposition product gas molecules, the excitation light is irradiated on the gas molecules to be measured, these gas molecules will absorb light energy and convert it into heat energy, the energy conversion process causes the gas molecules to heat up rapidly, and then produce a small pressure change in the air inlet cavity 411, the pressure fluctuation converted from light energy propagates in the first photoacoustic resonance tube 421 and the second photoacoustic resonance tube 422 to form a photoacoustic pressure wave, the photoacoustic pressure wave causes the cantilever beam of the cantilever beam sensor to vibrate, at this time, the detection light is input from two single-mode optical fibers, the end faces of the two single-mode optical fibers and the cantilever beam of the cantilever beam sensor form a Fabry-Perot cavity, the reflected light of the end face of the single-mode optical fiber interferes with the reflected light of the cantilever beam, the interference spectrum is demodulated by an instrument, and the SF can be detected. 6 The concentration of its decomposition products.

[0024] SF of the embodiment of the present invention 6 The principle analysis of how decomposition product monitoring photoacoustic gas sensors can reduce airflow noise is as follows: First, the SF of the embodiment of the present invention 6 The decomposition product monitoring photoacoustic gas sensor is structurally designed with a first photoacoustic resonance tube 421 and a second photoacoustic resonance tube 422. Since the two photoacoustic resonance tubes are exactly the same in size and shape, the photoacoustic signal amplitudes in the two photoacoustic resonance tubes are the same and the phases are opposite, while the amplitude and phase of the incoherent noise in the tubes are the same. The two cantilever sensors for detecting photoacoustic signals installed in the first cantilever beam sensor mounting hole 47 and the second cantilever beam sensor mounting hole 48 and the first photoacoustic resonance tube 421 and the second photoacoustic resonance tube 422 constitute a differential double-tube photoacoustic pool structure, which is beneficial to suppressing the influence of airflow noise.

[0025] Secondly, due to SF 6 The gas density is heavier than air. This high density and large molecular weight make SF 6 When gas flows, the collisions between molecules are more frequent and violent, thus generating greater noise. 6 The gas flow rate will also affect the size of the gas flow noise. Generally speaking, the greater the flow rate, the more intense the collision and friction between gas molecules, and the greater the airflow noise generated. Therefore, reducing gas flow noise is the key to achieving SF 6 The key to real-time online monitoring of decomposition products; in view of this problem, the SF 6 The first flow guide tube 423 and the second flow guide tube 424 designed for the decomposition product monitoring photoacoustic gas sensor are helpful to disperse the SF flowing into and out of the first photoacoustic resonance tube 421 and the second photoacoustic resonance tube 422. 6 The flow rate of the gas is such that the SF flowing into and out of the first photoacoustic resonance tube 421 and the second photoacoustic resonance tube 422 6The gas flow is smoother, avoiding the noise caused by excessive flow, and also reducing the flow noise caused by turbulence and vortexes during the gas flow.

[0026] like Fig.11 As shown, the one-time standard deviation noise of the gas measured in the fiber optic photoacoustic gas sensor without the guide tube is approximately equal to 1.2 pm, while after adding the guide tube, the measured one-time standard deviation noise can be reduced to about 0.17 pm, which greatly reduces the flow noise.

[0027] Embodiment 2 like Fig.12 As shown, the SF of the embodiment of the present invention 6 The decomposition product monitoring optical fiber photoacoustic gas sensing system comprises: a detection light source 1, an optical fiber coupler 2, an excitation light source 3, an optical fiber photoacoustic gas sensor 4, a high-speed spectrometer 5, a signal processing circuit 6, and a computer 7; the excitation light source 3 is connected to the optical fiber photoacoustic gas sensor 4 through an optical fiber collimator, the detection light source 1 is connected to the optical fiber coupler 2 through an optical fiber, the optical fiber coupler 2 uses two single-mode optical fibers to be respectively connected to the optical fiber photoacoustic gas sensor 4, the output end of the optical fiber coupler 2 is connected to the input end of the high-speed spectrometer 5, the output end of the high-speed spectrometer 5 is connected to the input end of the signal processing circuit 6, and the output end of the signal processing circuit 6 is connected to the input end of the computer 7.

[0028] Preferably, the wavelength range of the high-speed spectrometer 5 is 1525nm-1570nm, and the sampling frame rate is greater than 10kHz; the detection light source 1 adopts a broadband detection light source.

[0029] SF of the embodiment of the present invention 6 The workflow of the fiber optic photoacoustic gas sensing system for decomposition product monitoring is as follows: The excitation light emitted by the excitation light source 3 is incident on the fiber optic photoacoustic gas sensor 4 to excite the gas molecules to be measured. The detection light emitted by the detection light source 1 passes through the fiber optic coupler 2, and then enters the fiber optic photoacoustic gas sensor 4 through two single-mode optical fibers for differential detection. The detected differential interference spectrum signal is transmitted to the high-speed spectrometer 5 through the fiber optic coupler 2. The differential interference spectrum signal is processed by the signal processing circuit 6, and the processing result is displayed in the computer 7.

[0030] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fiber optic photoacoustic gas sensor for monitoring SF6 decomposition products, characterized in that: The open end of the air inlet buffer chamber is sealed and connected to one side of the differential double-tube photoacoustic pool structure, and the other side of the differential double-tube photoacoustic pool structure is sealed and connected to the open end of the air outlet buffer chamber; an excitation light source fiber collimator mounting hole is provided at one end of the air inlet cavity of the air inlet buffer chamber, and the other end of the air inlet cavity is open, and the air inlet hole processed on one side of the air inlet buffer chamber is connected to the air inlet cavity; two identical first photoacoustic resonance tubes, second photoacoustic resonance tubes, and multiple guide tubes are processed in the differential double-tube photoacoustic pool structure, and two cantilever beam sensor mounting holes are symmetrically processed at the center positions on both sides of the differential double-tube photoacoustic pool structure for installing cantilever beam sensors, and the cantilever beam sensors are respectively corresponding to the outer walls of the first photoacoustic resonance tube and the second photoacoustic resonance tube; one end of the air outlet cavity of the air outlet buffer chamber is closed, and the other end of the air outlet cavity is open, and the air outlet hole processed on one side of the air outlet buffer chamber is connected to the air outlet cavity.

2. The optical fiber photoacoustic gas sensor for monitoring SF6 decomposition products according to claim 1 is characterized in that: The diameter of the flow guide tube is larger than the diameter of the first photoacoustic resonance tube or the second photoacoustic resonance tube.

3. The optical fiber photoacoustic gas sensor for monitoring SF6 decomposition products according to claim 1, characterized in that: The first photoacoustic resonance tube and the second photoacoustic resonance tube are arranged symmetrically with respect to the xoz plane.

4. The optical fiber photoacoustic gas sensor for monitoring SF6 decomposition products according to claim 1, characterized in that: Also includes: The optical fiber collimator is installed in the optical fiber collimator installation hole of the excitation light source.

5. The optical fiber photoacoustic gas sensor for monitoring SF6 decomposition products according to claim 1, characterized in that: The two single-mode optical fibers are respectively connected to the cantilever beam sensors installed in the first cantilever beam sensor installation hole and the second cantilever beam sensor installation hole.

6. A method for using the optical fiber photoacoustic gas sensor for monitoring SF6 decomposition products as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: 1) SF6 decomposition products enter the gas cavity from the air inlet, flow into the gas outlet cavity through the first photoacoustic resonance tube, the second photoacoustic resonance tube and the guide tube in the differential double-tube photoacoustic cell structure, and then flow out through the air outlet; 2) The excitation light is incident into the air inlet cavity through the optical fiber collimator. The excitation light excites the gas molecules of the SF6 decomposition product in the air inlet cavity, propagates in the first photoacoustic resonance tube and the second photoacoustic resonance tube to form a photoacoustic pressure wave, which causes the cantilever beam of the cantilever beam sensor to vibrate; 3) The detection light is input from two single-mode optical fibers. The end faces of the two single-mode optical fibers and the cantilever beam of the cantilever beam sensor form a Fabry-Perot cavity. The reflected light from the end faces of the single-mode optical fibers interferes with the reflected light from the cantilever beam. The interference spectrum is demodulated by an instrument to detect the concentration of SF6 decomposition products.

7. An optical fiber photoacoustic gas sensing system for monitoring SF6 decomposition products, characterized in that: include: A detection light source, a fiber optic coupler, an excitation light source, a high-speed spectrometer, a signal processing circuit, and a computer; the excitation light source is connected to the fiber optic photoacoustic gas sensor according to any one of claims 1 to 5 through a fiber optic collimator, the detection light source is connected to the fiber optic coupler through an optical fiber, the fiber optic coupler uses two single-mode optical fibers to be respectively connected to the fiber optic photoacoustic gas sensor, the output end of the fiber optic coupler is connected to the input end of the high-speed spectrometer, the output end of the high-speed spectrometer is connected to the input end of the signal processing circuit, and the output end of the signal processing circuit is connected to the input end of the computer.

8. The optical fiber photoacoustic gas sensing system for monitoring SF6 decomposition products according to claim 7 is characterized in that: The working process is as follows: the excitation light emitted by the excitation light source is incident on the fiber optic photoacoustic gas sensor to excite the gas molecules to be measured. The detection light emitted by the detection light source passes through the fiber optic coupler and then enters the fiber optic photoacoustic gas sensor through two single-mode optical fibers for differential detection. The detected differential interference spectrum signal is transmitted to the high-speed spectrometer through the fiber optic coupler. The differential interference spectrum signal is processed by the signal processing circuit, and the processing result is displayed on the computer.

9. The optical fiber photoacoustic gas sensing system for monitoring SF6 decomposition products according to claim 7, characterized in that: The wavelength range of the high-speed spectrometer is 1525nm-1570nm, and the sampling frame rate is greater than 10kHz.

10. The optical fiber photoacoustic gas sensing system for monitoring SF6 decomposition products according to claim 7, characterized in that: The detection light source adopts a broadband detection light source.

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