Dual Fiber-Optic Microphone Based on Coherent Synthesis Technology

Abstract

This paper proposes a dual fiber-optic microphone (DFOM) based on coherent synthesis technology, in which the sound pickup module mainly consists of two optical fibers and a reflection film, constituting two identical Fabry-Perot (FP) interferometric cavities as the acoustic sensing structure. The use of dual fiber-optic can increase the light intensity of the reflected light received by the photodetector (PD), while offsetting signal distortion caused by factors such as fiber length and temperature variations, and reducing signal interference, thereby improving the purity and accuracy of the signal. The DFOM exhibits strong fault tolerance, in case one of the optical fibers fails, the other one can still perform normal sound collection, thus enhancing the reliability of the microphone. Acoustic tests show that the sound pressure sensitivity of this DFOM at a frequency of 250 Hz is 64.8 mV/Pa. The signal-to-noise ratio (SNR) is as high as 62.45 dB under the action of a 6 kHz sound pressure signal. It maintains a linear sound pressure response and a flat frequency response in the range of 10 Hz to 20 kHz. These results indicate that the DFOM has high sensitivity and a wide frequency response range, making it suitable for acoustic detection within the audible range.