Noise reduction with adaptive filtering scheme on interferometric fiber optic hydrophone

Fiber optic hydrophones have been widely used in underwater sounding, vibration detection and marine geological exploration due to their high sensitivity, wide frequency response range and strong anti-electromagnetic interference capability. In this paper, an adaptive filtering scheme based on Least Mean Square algorithm (LMS) is proposed to improve the detection sensitivity of hydrophones. Aiming to eliminate noise interference, a reference interferometer with the same parameters as the signal interferometer is added to the optical structure. Then, two 3 x 3 couplers are placed to demodulate the sensing signal and the noise signal respectively. Finally the adaptive filtering process is adopted to eliminate the noise effectively. The experimental results show that the proposed scheme can reduce the harmonic distortion signal and the noise signal. The suppression capability of the harmonic distortion signals at 1000 Hz is about 19 dB, and the signal-to-noise ratio is improved by about 23 dB.