Demodulation method to suppress the influence of laser intensity disturbance in optical fiber hydrophone system

A novel demodulation method called nonlinear function scheme and realized by Lookup Table (LUT) technique was proposed in the optical fiber hydrophone array based on the spatial division multiplexing optoelectronic system for the application of oceanic oil exploration. The nonlinear function was obtained by dividing two channels of PGC interference detection signal. Compared with the traditional manner using arctangent algorithm to the linear combination of the two channels of detection signal, the nonlinear function scheme not only can compensate an effect of accompanying laser intensity modulation caused by direct alternating current injection to the DFB laser, but has the characteristic of suppressing an influence of random laser intensity disturbance on the PGC system using constant parameters to demodulate as well. Experimental results demonstrate that in the condition of directly modulating DFB laser, the nonlinear function demodulation scheme has an overwhelming superiority over the linear combination method in harmonic suppression performance and the difference of HSR mean value between the two demodulation schemes reaches 26.37 dB. When intensity in the system decreases by 50%, HSR mean value of the nonlinear function demodulation is larger than that of the linear combination and the difference reaches 17.53 dB.