Research On Noise Character Based On Matched Interferometric Fiber Optic Hydrophone Array

With the further application of fiber optic hydrophone in commercial,military and other fields,it is developing in the direction of large scale array and long-distance transmission.A variety of linear and nonlinear noise following can not be ignored.In this paper,we focus on the noise characteristics of the long distance matched interferometric fiber optic hydrophone array,especially on the Double Rayleigh Scattering(DRS)noise and the disturbance noise in the transmission fiber.Above this,a noise suppression method is carried out to improve the performance of the fiber optic hydrophone array.Firstly,comparing with the well-developed structure which consists of the independent Michelson interferometer,the advantages of the matched interferometric fiber optic hydrophone array are discussed.In this paper,we constructed a simplified TDM system.In view of the structure characteristics of the matched interferometer,a two way signal demodulation scheme based on 3×3 coupler is proposed,and the scheme of PGC demodulation is also used in the following experiments.Secondly,the theoretical analysis of the model of DRS noise is carried out.Furthermore,the conclusion that DRS noise is introduced into the system by means of the generating beat noise.By applying the frequency modulation of the light source,and combining the PGC algorithm and the self characteristics of the two channel demodulation algorithm based on the 3×3 coupler,the effect of DRS noise on the system is eliminated.Finally,the theoretical analysis and experimental test of the disturbance noise of the transmission fiber are carried out.By the introduction of the reference element in the fiber optic hydrophone array,the disturbance noise of the transmission fiber is suppressed by the demodulation algorithm based on the reference unit,and the inhibition rate of 10 dB is achieved above 100 Hz.