Abstract:

In order to solve the problem that traditional acoustic-electric microphone is susceptible to corrosion and electromagnetic interference,an acoustic-optic transducer structure which uses optical fiber to extract the sound is proposed.In this paper,the sensor prototype is based on Sagnac interferometer,the sound pressure is used to act on photo-elastic effect which generated by the optical fiber to achieve light-phase modulation,and a 3 × 3 coupler is used to build dual optical path balanced detection system.The demodulation of the speech signal is done through interference,which can realize two equal amplitude' signals differential processing,eliminating common mode interference signal and reducing light source noise.The experiments show that the system is stable with small waveform distortion.Voice signal extraction and restoration are implemented successfully in the range of 300~3 400 Hz.

Key words: microphone;Sagnac interferometer;photo elastic effect;dual optical balanced detection;3 ×, 3 coupler