Three-component homovibrational vector hydrophone based on fiber Bragg grating F-P interferometry.

A fiber optic vector hydrophone is an interesting topic for many applications. Using a fiber Bragg grating (FBG) as a reflection unit, the vector hydrophone combines the advantages of miniaturization, high reliability, and low cost. In this paper, the interferometric vector sensing, multiplexing design, and cross-talk suppression of a fiber optic vector hydrophone based on FBG-based Fabry-Perot interferometry are discussed and validated. The average cross talk of the channels is reduced by 20 dB than that of a high-reflectivity grating by using 1% reflectivity fiber gratings. A three-component homovibrational vector hydrophone with a low-reflection FBG was developed and tested. The working band of the hydrophone is extended to 20 Hz, and the sensitivity of each vector channel is about -132.5  dB at 500 Hz and its directivity index is more than 30 dB at 100 Hz.