Optimizing the sensitivity of a fiber optic-based Sagnac interferometer for high-performance human voice sensing

Abstract

This article presents a theoretical and experimental study aimed at enhancing the sensitivity of the fiber optic Sagnac interferometer, specifically designed for efficient detection of human voice signals. The study focuses on optimizing various factors that influence the sensitivity, including the frequency response of the Sagnac interferometer, the structure of the sensing fiber, and the sensor noise. Several fiber sensing structures were investigated both theoretically and experimentally within this framework to enable high-performance human voice sensing. The measurement results validate the theoretical findings, particularly highlighting the directional sensitivity influenced by the geometry of the sensing fiber structure. Notably, we succeeded in recording and intelligible listening to a human conversation at a distance of 5 m using a multi-layer fiber coil with a total length of 50 m. The measured Minimum Detectable Pressure (MDP) is approximately 337 μPa/Hz1/2 at 1 kHz, which can be reduced by increasing the fiber length.