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.
