Real-time Estimation Method of Normalized Parameter for PGC Demodulation of Optical Fiber Hydrophone

A real-time estimation method of normalized parameter is proposed to reduce the significant distortion in phase generated carrier(PGC) demodulation of optical fiber hydrophone due to offline estimation of normalized pa-rameter. The square differences of the amplitudes of two orthogonal signals at both current time point and previous time point are calculated, then the normalized parameter is obtained by calculating the ratio of two square differences. Simu-lations and experiments show that a correct normalized parameter can be achieved with the proposed method if signal amplitude is small. Experimental results indicate that when a small signal with peak amplitude of 0.3 radian is imposed to the hydrophone, the estimation error of normalized parameter gets less than 3%. Using the achieved normalized pa-rameter to demodulate the signal of the optical fiber hydrophone, signal to total harmonic distortion ratio is less than 48 dB, which meets the requirement for engineering application.