Fiber bragg grating hydrophone array using multi-wavelength laser: simultaneous multipoint underwater acoustic detection

Abstract

A novel fiber Bragg grating (FBG) hydrophone array is proposed in order to realize simultaneous multipoint underwater acoustic detection with thermal stabilization. The interrogation technique of the FBG hydrophone to be arrayed is based on an intensity-modulation scheme, in which a tunable laser is used for an optical source with its oscillation wavelength tuned to a slope of the reflection spectrum curve of the FBG. The light reflected at the sensing FBG is modulated by an underwater acoustic wave and offers a waveform signal as a sensor output. For fabricating the FBG hydrophone array, a multi-wavelength tunable fiber laser is constructed for providing multiple narrowband optical sources and the sensing FBGs are arranged in tandem using a wavelength-division multiplexing (WDM) technique. In the experiment, simultaneous three-point underwater acoustic detection and measurement of sound velocity in water have been successfully demonstrated.