Measuring the frequency response of an optical microphone system with a fiber based setup

Abstract This paper presents a measurement method for characterizing the frequency response of an optical microphone system using a purely optical approach. The use of optical methods allows to precisely determine the frequency response of the device from infra-sound up to 100 kHz in a single measurement, without the need of a reference microphone. The presented method relies on the inherently flat frequency characteristics of an optical cavity, allowing the assignment of any frequency-dependent behavior to secondary sources, such as the signal conditioning and data acquisition unit. The frequency characteristic was found to be strongly dependent on the settings of the internal amplifiers and high-pass filters, indicating the necessity of a calibration procedure if a flat frequency response is required.