Abstract: The optical fiber sensor is a new type of sensor developed in the mid-1970s, in comparison with or- dinary sensors, it has the advantages of high sensitivity, anti-electromagnetic interference, corrosion resistance, anti -burning, etc. Therefore, it is widely used in the sensor field of temperature, stress, magnetic. In this paper, a fiber-optic acoustic sensor is studied, which is based on an all-fiber interferometer, the main technical focuses on production of the probe in the sensing arm. By single-mode fiber acoustic sensor based on Mach - Zehnder in- terferometer, the frequency of sound waves and the sound pressure level （the output voltage difference between peak and trough） can be measured. The frequency response range is 4 N 5000 I-lz, covering the infrasound band, however, which is difficult for ordinary acoustic sensors to achieve. The upper limit of linear response range is 100 dBA.

Key words: sensors, a fiber acoustic sensor, phase modulation, M-Z all-fiber interferometer