Mechanical and optical optimization of a fiber-optic interferometric acoustic sensor

Abstract

External cavity Fiber optic interferometric microphones have the potential to operate at the acustic impedance derived noise limit, with a noise oor close to 1uPa=pHz. This can be achieved with careful optimization of both the mechanical and optical properties of such a sensor. We describe models for the acoustic-to-displacement and displacement-to-optical signal transduction in a Fabry-Perot (FP) type interferometric microphone. We present experimental results and nite element calculations to validate the models. Based on the models, requirements to achieve ultimate sensitivity and noise level in a FP microphone are discussed. Demonstration of a microphone with 30 dBA noise foor is presented using partially optimized membrane and interferometer.