The ring-type all-fiber Fabry–Pérot interferometer hydrophone system

Abstract

A compact theory and the detailed design of the ring-type all-fiber Fabry–Pérot interferometer hydrophone system has been developed here. The system is composed of four parts: the optical part with the laser source, the ring interferometer of all-fiber suited for the acoustical structure, the acoustical structure, and the stabilization maintaining the feedback servo mechanism and signal demodulation part. For this reason it differs greatly in many ways from the traditional concept of hydrophone which is commonly made up with one or several functional material elements such as the piezoelectric ceramic or the PVDF ones. So, on accuracy ground it is named the Fiber Hydrophone System instead of Hydrophone. The fiber-optic hydrophone itself, not including the laser source and the electric servo part, has the compact size of φ40×80 mm, specific gravity of less than 1, and the system has a free-field open-circuit voltage sensitivity level of above −140 dB re: 1 V/μPa. Experimental results show an exciting future of this kind of fiber-optic hydrophone system for the application of all optical towed arrays.