Research On Preparation Of Graphene Oxide Films And Their Application In Fiber-Optic Fabry-Perot Sound-Pressure Sensing

Power equipment such as transformers can generate strong noise signals during operation,and corona discharge and some insulation faults can also generate acoustic signals of different intensities when they occur.The high-quality detection of these acoustic signals(20 Hz-20 k Hz)that can be heard by human ears has always been the focus of research in the field of electrical sensing and measurement.Although traditional electromagnetic microphones can detect these acoustic signals,they have always had disadvantages such as susceptibility to electromagnetic interference,poor electrical insulation performance,and low detection sensitivity.However,extrinsic fiber-optic Fabry-Perot sound-pressure sensors have inherent advantages such as anti-electromagnetic interference,great electrical insulation performance and so on,so it is very suitable for audible sound detection of electrical equipment to replace traditional electromagnetic microphones.In addition,because graphene oxide films as poor conductors have the characteristics of strong flexibility,easy adsorption,and easy combination with optical fibers,it is very suitable for application in fiber-optic sensors based on flexible film mechanical vibration.Therefore,in this thesis,a graphene oxide film is selected as the sensing diaphragm,and an extrinsic fiber-optic Fabry-Perot sound-pressure sensor with excellent performance is developed.The main content of this thesis is as follows:(1)A method for preparing graphene oxide dispersion to make the dispersion more stable is proposed,and the mathematical expression between the concentration of graphene oxide dispersion and the thickness of graphene oxide films is established,and a set of graphene oxide film preparation process is summarized,which is time-saving,efficient,and thickness-controllable.(2)The size and structure of the sensing probe of the proposed fiber-optic Fabry-Perot sound-pressure sensor is designed and selected,and graphene oxide films without substrates are prepared by chemical etching method,and the efficient transfer of films is realized.In addition,the length of Fabry–Perot cavity is derived and calculated to be approximately 45 ?m,and the incident laser wavelength is derived and calculated to be around 1545.06 nm,and according to the calculation results,an extrinsic fiber-optic Fabry-Perot sound-pressure sensor based on a graphene oxide film whose thickness and effective vibration diameter is approximately 500 nm and 4.377 mm,respectively,is fabricated.(3)A performance test platform for sound-pressure sensors is built,and the performance of the proposed fiber-optic Fabry-Perot sound-pressure sensor is tested.The test results show that the proposed sensor has a linearly sound-pressure response characteristics,a flat frequency response characteristics and an average sensitivity of24.48 m V/Pa in the frequency range of 20 Hz-20 k Hz.And the sensor has uniform directional response characteristics and a higher long-term working stability.In addition,the proposed sensor also has an exponentially decayed distance response characteristic and a response time characteristic that increases linearly with distance,and the sensitivity of the sensor's response time to distance is 2.247 ms/cm.In this thesis,Graphene oxide film preparation methods,sensor designing and manufacturing methods,sensor performance testing and analysis methods all provide a valuable reference for the real application of extrinsic fiber-optic Fabry–Perot sound-pressure sensors instead of electromagnetic microphones in the audible sound detection of electrical equipment.