A four-element optical fiber 4C vector hydrophone array

A horizontal line array of four component (4C) optical fiber vector hydrophones (OFVHs) has been developed for underwater ambient noise measurement and direction-of-arrival (DOA) estimation of underwater target. The OFVH array consists of four OFVHs spaced uniformly over a 3 meter horizontal aperture, and each OFVH package having its own compass. The noise floor of the OFVH array achieves -100 dB/Hz1/2 at 1000 Hz. The OFVH is composed of a threecomponent optical fiber accelerometer with the phase sensitivities of three axes about -155 dB re rad/μPa at 1000 Hz and an optical fiber hydrophone with the phase sensitivity -144.3 dB re rad/μPa over the frequency range from 20 Hz to 2000 Hz. A sea trial of the OFVH array has been successfully carried out in South China Sea. The trial results show that the OFVH array can remove the 180° ambiguity in the DOA estimation by using the information of particle velocity of the sound, and the DOA estimation accuracy obviously excelled the single OFVH and optical fiber hydrophone array. The excellent performance of the OFVH array for use in target passive DOA estimation and tracking is proved by results.