Study On The Development Of Reflective Fiber Optical Acoustic Sensor System And Its Performance Testing Method

Fiber optic acoustic sensor (FOAS) has many excellences such as anti-EMI,anti-RFI, wide frequency range, high sensitivity, fine resistant to corrosion, strongconfidentiality, high reliability, simple structure, small volume. So it was widely usedin measuring the voice in strong electromagnetic field, high radio frequencyinterference environment, and it also used in medicine, military, inflammable andexplosive field, etc. At present, the research of FOAS is focused on the formula of thelight intensity modulating. So develop a fiber optic acoustic sensor of high stability,good property has the valuable significance. And in the development of FOAS, sensorprobe’s mechanical design, sensor’s light intensity compensation, the vibrationmembrane’s choice and the optoelectronic processing circuit’s design are relation tothe sensor’s performance. Based on the above several key technologies, the FOASwas developed. Also experimental platform was build to test the sensor’sperformance.This paper redesigned the RIM-FOAS’s sensing probe, opened two holes in theprobe’s back plate. So the reaction pressure from the motion of the membrane canrelieved by the air flow through the two holes. The two holes decreased the dampingof the coupled membrane-air layer system. Also this paper gave the model of probe’stheory formula and flow field analysis. It realizes the light intensity compensation bymeasuring circuit signal’s divided by the reference optical path’s signal. According tothe intensity compensation to the symmetry of photoelectric detection circuitrequirements, the compensation circuit was designed. And experiment results showthat this method can compensate power fluctuations and the temperature drift whichbring by the sensor’s work long hours. The vibration membrane was using FEP whichsurface silver. Among these, sensor probe’s mechanical design and its flow fieldanalysis, sensor’s light intensity compensation, are the most important features of thisarticle.Related performance test was toke after the sensor’s design. The experimentalresults suggest that the sensor’s sensitivity is found to be550mV/Pa, nonlinear erroris1.9%and the measurement range lies within50Hz~10000Hz within-3dBbandwidth. Experiment result proved the sensor probe’s stability and the scheme’sfeasibility.