Research On The Sensing Mechanism And Devices Of Optical Fiber MOEMS Acoustic Sensor

Optical fiber acoustic sensor has been widely studied since it first appeared in 1970s because of its small size,anti-electromagnetic interference,low transmission loss,corrosion resistance and safety and reliability.On the other hand,the MEMS acoustic sensor also has been extensively reported and used in acoustic detection.The products processed by MEMS technology have the advantages of small size,light weight,high integration and easy mass production.Micro-acoustic sensors can be integrated on a single silicon chip by using the MEMS processing technology.Compared with traditional electrical microphone,it has the advantages of high device integration and low power consumption.However,the existing MEMS acoustic sensors are mainly based on the principle of capacitive signal detection.The sensor has low sensitivity and is vulnerable to external electromagnetic interference,which seriously restricts the application of the MEMS acoustic sensors in high sensitivity acoustic detection and extreme environment.In this paper,a high-sensitivity acoustic signal detection structure is realized by combining MEMS acoustic sensitive components and fiber Fabry-Perot?F-P?structure.The MEMS acoustic sensitive film has high sensitivity to sound pressure detection,flexible structure design,good consistency of preparation process and it can realize the effective detection of weak sound pressure signal by combining with the fiber F-P optical signal detection method.Moreover,the fiber acoustic sensing structure has the characteristics of passivity and anti-electromagnetic interference and has very wide application prospects in the detection of sound or vibration signals in some extreme environments?such as high-voltage substation,etc?.Therefore,this paper proposes a fiber-optic F-P acoustic sensor based on MEMS film,and carries out systematic research work on it.The main contents are as follows:This paper first introduces the research status of fiber-optic acoustic sensor and MEMS acoustic sensor,then introduces the excellent characteristics of MEMS film and its stress simulation analysis,and proposes to use MEMS silicon nitride film as sound pressure sensitive film and combines it with the single-mode fiber end face to form the fiber F-P cavity for acoustic sensing.At the same time,the designed periodic annular corrugated MEMS diaphragm is used to enhance the sensitivity of acoustic detection.This provides a theoretical basis for the subsequent fabrication of fiber-optic acoustic sensor.Next,we introduce the working principle and fabrication process of the fiber-optic acoustic sensor in detail,including the fabrication of MEMS film and the fabrication of the fiber-optic acoustic probe.Then,we connect the sensor to the fiber-optic acoustic detection system,and test and compare the performance of the fiber-optic F-P acoustic sensors based on different MEMS film parameters from the aspects of response characteristics,signal-to-noise ratio and sensitivity,and compare them with the traditional electronic microphone.Finally,the paper also proposes some optimization suggestions from the aspects of the preparation process of the film and the structure of the fiber-optic acoustic probe.The experimental results show that the fiber-optic Fabry-Perot sensor based on the periodic annular corrugated MEMS film has higher sensitivity than the traditional electrical microphone?50mV/Pa?,and its sound pressure sensitivity at 1kHz is as high as 2.23V/Pa.Its signal-to-noise ratio is as high as 79.08dB,and the corresponding minimum detectable pressure is as high as 2.97?Pa/Hz^1/2,which is more than 20 times higher than the sensitivity of the electronic microphone.It can detect weaker sound signals,and the reduction effect on external sound signals is also ideal.Besides,it also has the advantages of good consistency and low temperature drift.It can be integrated in the multiplexing fiber-optic sensing scheme with a single interrogation system to achieve an acoustic array sensors.