A fiber-optical microphone based on a Fabry–Perot interferometer applied for thermo-acoustic measurements

Abstract

A high-temperature resistant fiber-optical microphone (FOM) was developed and successfully applied in a combustion chamber (∼1.2 × 105 Pa, ∼1400 K gas temperature) with thermo-acoustic oscillations resulting in a sound pressure level of 154 dB at the dominant frequency. The core of the optical set-up used for the FOM is a Fabry–Perot interferometer. To create an acoustical sensor based on this type of interferometer, a new method of generation and postprocessing of the interference signal was developed. The simple replaceability of the used membrane material allows the adaptation of the sensor sensitivity to the projected field of application.