Research And Application Of Optical Fiber MOEMS Ultrasonic Sensor

This paper studies a fiber optic MOEMS ultrasonic sensor based on the Fabry-Perot interference structure.This sensor structure combines MOEMS technology with fiber optic ultrasonic sensing technology.In the detection of ultrasonic signals,it has the advantages of high sensitivity,large signal-to-noise ratio,good frequency bandwidth and good consistency.The research in this paper provides a new technical method for passive online monitoring of ultrasound in engineering applications.Firstly,the thesis analyzes and studies the optical fiber ultrasonic sensing technology based on different structures,and clarifies the structural advantages of the interferometric optical fiber ultrasonic sensing.The development,process and application of MOEMS technology are introduced,which provides support for the application of MOEMS technology in the production of optical fiber ultrasonic sensors.Carried out research on the characteristics of silicon nitride materials,because the material has higher elastic modulus,excellent dimensional stability,corrosion resistance and non-magnetic advantages,so it is used as a sound pressure sensitive material in this paper.On the basis of the structure of the interferometric sensor,this paper optimizes the design of the diaphragm structure to reduce the limitation of the sensitivity of the residual stress to its sound pressure response.Through the finite element simulation of this kind of diaphragm structure,a ring-shaped corrugated structure is designed,which can significantly increase the displacement of the central sensing area of the diaphragm under the effect of sound pressure,and the experiment proves that the structure can be improved Response sensitivity of ultrasonic sensing.Secondly,this paper carried out a performance study based on the optical fiber MOEMS ultrasonic sensor,and studied the main parameters such as the time domain response characteristics,frequency domain response bandwidth,signal-to-noise ratio directivity,and response linearity of the sensor.Through comparative experimental tests on various ring-shaped thin film structures,the optimized diaphragm structure parameters based on the ultrasonic sensor were finally obtained: the diaphragm thickness was 400 nm,and the number of corrugated rings was 1 ring.Finally,this paper conducted an experimental study on the application of the optical fiber MOEMS ultrasonic sensor in partial discharge signal detection.In the experiment,through the comparative test with commercial electrical sensors.It can be seen from the detection results that the achievable sound pressure sensitivity of the optical fiber MOEMS ultrasonic sensor is much higher than that of the reference electrical sensor,the minimum detection sound pressure is,the frequency response bandwidth is 20kHz-470 kHz,which can meet the frequency bandwidth requirements of partial discharge detection.Therefore,the optical fiber MOEMS ultrasonic sensor studied in this paper has good application potential in the field of on-line monitoring of partial discharge of power equipment such as cable contacts and transformers.