Ultrathin interferometric hydrophone towed line array based on uwFBG

Abstract

In order to improve the suitability of the fiber hydrophone towing line array, we propose an interferometric hydrophone towed line array with a diameter of 1.7 mm. The line array is an integration of sensitization and package, embedding grating sensors in the composite materials of Kevlar and polyurethane in an additional pultrusion process. The theory and experiment indicate that polymer cladding of pultrusion is an effective way to improve phase sensitivity, increasing mechanical strength and decreasing cable diameter simultaneously. Then, a hydroacoustic detection system, with a quasi-distributed ultra-weak fiber Bragg grating towed line array, based on unbalanced interference is established and its phase sensitivities are tested experimentally. The result is measured by the vibration liquid column method and compared with a standard piezoelectric underwater acoustic detector. Over the frequency range of 200–2000 Hz, the system has a good amplitude–frequency response. We obtain an average phase sound pressure sensitivity of about −147.96 dB (re 1 rad/μPa) and a relative flatness response of 3 dB. The experimental results show that this system provides the possibility of an integrated hydrophone towed linear array with high adaptability and reliability.