Analysis of phase response of fiber Fabry-Pérot cavity microphones.

Abstract

In this paper, the phase response of fiber Fabry-Pérot cavity-based fiber optic microphones (FFPC-FOMs) is discussed through an analysis of the results of simulation and experiments. The phase difference of FFPC-FOMs mainly originates from two aspects: different phase lags of the mechanical-acoustic systems and different quadrature working points (Q*) on interference curves. The former is analyzed by an impedance-type analogous circuit, and the simulation results reveal that the change in cavity length and resonance frequency in a large range have an insignificant influence on the phase difference. The latter shows a unique effect on the phase difference and causes the phase of FFPC-FOMs to be either in or out of phase. The phase differences of four samples of FFPC-FOMs with different cavity lengths and resonance frequencies are measured in the frequency range 50 Hz-4 kHz. Experimental results of the phase difference are well consistent with simulation results. All samples of FFPC-FOMs can be divided into two groups: one is near 0° and the other is near 180°. In addition, the FFPC-FOMs in each group have good phase consistency for the array applications.