Investigation on a pressure-gradient fiber laser hydrophone

Abstract

In this paper, a pressure-gradient fiber laser hydrophone is demonstrated. Two brass diaphragms are installed at the end of a metal cylinder as sensing elements. A distributed feedback fiber laser, fixed at the center of the two diaphragms, is elongated or shortened due to the acoustic wave. There are two orifices at the middle of the cylinder. So this structure can work as a pressure-gradient microphone in the acoustic field. Furthermore, the hydrostatic pressure is self-compensated and an ultra-thin dimension is achieved. Theoretical analysis is given based on the electro-acoustic theory. Field trials are carried out to test the performance of the hydrophone. A sensitivity of 100 nm MPa −1 has been achieved. Due to the small dimensions, no directivity is found in the test.

Fiber laser sensing system and its applications

“…Hence, pressure gradient structure is introduced in enhancing the sensitivity of FLH and compensating the hydrostatic pressure [40]. Owing to the orifice at the sensor shell, the water can enter into the sensor and the hydrostatic pressure is compensated while an ultra-high sensitivity has been achieved.…”

分布反馈式光纤激光水听器探头封装及应用研究进展

“…11 DFB fiber laser hydrophone with static pressure compensation function. (a) Structural drawing; (b) physical drawing [21][22] 图 12 DFB 光纤激光水听器的应用。 (a)批量封装实物图； (b)水听器阵列对目标的方位历程图 ［26］ Fig. 12 Application of the DFB fiber laser hydrophone.…”