Improvement of Noise Stability of Michelson Optical Fiber Voice Monitoring System

Abstract

Optical fiber sensing is a novel sensing technology with the advantages of antielectromagnetic interference, anti-corrosion and high sensitivity suiting for many special applications. In this paper, a Michelson optical fiber voice monitoring system is introduced and a novel sound extraction algorithm is proposed to improve the noise stability of it. The voice demodulated by a traditional algorithm based on 3×3 fiber coupler has unstable background noise intensity with the change of the working point of the interferometer. The unstable noise comes from the shot noise of photodetectors. The sound extraction method proposed in this paper uses the relation between shot noise and light intensity to smooth the unstable noise and does not affect the quality of voice monitoring. Voice monitoring systems using this algorithm have stable monitoring quality without any working point control technology. The fluctuation range of noise intensity in 300 ~ 3500 Hz decrease from 10 dB to less than 2 dB compared with the traditional demodulation algorithm. Such a method and system can be widely used in many special voice monitoring application fields such as prison, underground utility tunnel.

Characterization of sensitivity of optical fiber cables to acoustic vibrations

“…Implementations in sensing seismic vibration have been also reported 28 as well as possible use in monitoring of marine structures 29 . It is also worth noting that research is carried out that deals with improving the noise stability of the MI 30 . The star topology of the fiber optic infrastructure inside buildings gives the opportunity to build the MI arrangement.…”