A novel fiber optic interferometer of hydrophone based on Mach-Zehnder hybrid configuration

Abstract

We report on the development of a new type of hydrophone based on an optical fiber interferometer sensor. This interferometer based on dual Sagnac ring configuration to pick up the underwater acoustic signal. Using the unbalanced arms of the Mach-Zehnder interferometer (MZI), the underwater acoustic wave induces the phase difference on optic fiber hydrophone interrogator to demodulate the acoustic field signals by PGC modulation circuit. The configuration is easily implemented and can detect weak signal in a high noisy water environment. The underwater hydrophone systems primarily with B&K system, projector 8104 and receiver 8103, have been successfully worked. As well, B&K 8104 acoustic response increases with frequency but also causes the echo noise in the meantime. The experimental results show that over the frequency range of 7 to 11 KHz, the hydrophone has an almost flat response with an average sensitivity and dynamic range of -211.47 dB re/µPa and 33dB, respectively.