Research On High Sensitivity Diffuse Fiber-Optical Photoacoustic Gas Sensor

With the continuous expansion of economic development and industrial scale,a wide variety of gases are playing an increasingly important role in industrial production.There are a large number of flammable,explosive and toxic and harmful gases in these gases.Enrichment of dangerous gases may cause huge hazards such as fires and explosions.However,the leakage of trace gases,especially the leakage of colorless and odorless gases,is often difficult to detect.Selecting a high-sensitivity gas detection program to detect problems in the early stages of leakage and determine the type of failure is of great significance to avoiding the above-mentioned hazardous accidents.This article focuses on the design of a high-sensitivity miniaturized optical fiber photoacoustic sensor and analyzes the stability of the gas detection results.In order to improve the gas detection sensitivity of the optical fiber photoacoustic sensor,this paper deeply analyzes the physical characteristics of the optical fiber Fabry-Perot(F-P)acoustic wave sensor,optimizes the acoustic wave sensor according to the sound pressure response characteristics,and designs and manufactures a miniaturized optical fiber optical sensor.Acoustic sensor.And explored the preparation method of the stainless steel cantilever acoustic wave sensor,combined with the cantilever beam optical fiber F-P acoustic wave sensor and photoacoustic spectroscopy gas detection technology,the sensor has a sensitivity of2251 nm/Pa at the resonance frequency.Compared with the resonant photoacoustic cell,the miniaturized optical fiber sensor is more adaptable to the narrow and harsh use environment and the places that require long-distance telemetry.The miniaturized sensor adopts a diffusion type ventilation mechanism,and uses the small hole diffusion method for gas exchange.It does not require a solenoid valve to control the gas flow,and realizes all-optical gas detection,which greatly reduces the system response time while being intrinsically safe.At the same time,the diffusio n hole of the optical fiber sensor also has the effect of isolating high frequency noise from the outside,so that the sound-sensitive structure cantilever beam is not directly exposed to the gas environment,which improves the stability and life of the optical fiber sensor.The Fluent fluid simulation software and the COMSOL acoustic simulation module were used to analyze the response time and sound insulation and noise reduction functions of the system,and further optimize the sensor structure and size parameters.Finally,the temperature characteristics of the cantilever optical fiber F-P acoustic wave sensor and the temperature effect of the photoacoustic signal are analyzed,and the characteristics of the frequency response curve of the optical fiber sensor with temperature drift are verified,and the temperature self-compensation of the optical fiber photoacoustic gas detection technology is realized.Find the temperature-insensitive point of the optical fiber photoacoustic sensor,and adopt the wavelength modulation method.When the temperature changes,the measurement error of the gas detection at the working frequency is greatly reduced,and the stability of the measurement result is further improved.Finally,the built photoacoustic spectroscopy gas detection system was used to test acetylene(C₂H₂)and methane gas respectively.Using white light interference demodulation algorithm,when the integration time is 1 s,the detection limit of CH₄ and C₂H₂ gas reaches 1.41 ppm and 60 ppb,respectively,realizing the high sensitivity of the miniaturized optical fiber photoacoustic gas sensor to trace gases,High stability detection.