Research on the Frequency Response and Dynamic Range of the Quadrature Fiber Optic Fabry–Perot Cavity Microphone Based on the Differential Cross Multiplication Demodulation Algorithm

A quadrature fiber optic Fabry–Perot cavity microphone based on a differential cross multiplication algorithm consists of a pair of fibers and a membrane. It has many advantages such as high sensitivity, a simple structure, and resistance to electromagnetic interference. However, there are no systematic studies on its key performance, for example, its frequency response and dynamic range. In this paper, a comprehensive study of these two key parameters is carried out using simulation analysis and experimental verification. The upper limit of the frequency response range and the upper limit of the dynamic range influence each other, and they are both affected by the data sampling rate. At a certain data sampling rate, the higher the upper limit of the frequency response range is the lower the upper limit of the dynamic range. The quantitative relationship between them is revealed. In addition, these two key parameters also are affected by the quadrature phase deviation. The quadrature phase deviation should not exceed 0.25π under the condition that the demodulated signal intensity is not attenuated by more than 3 dB. Subsequently, a short-step quadrature Fabry–Perot cavity method is proposed, which can suppress the quadrature phase deviation of the quadrature fiber optic Fabry–Perot cavity microphone based on the differential cross multiplication algorithm.