Study On Suppression Algorithm For The Noise Caused By The Leading Fiber Of Optical Fiber Hydrophone Array Based On Fiber Bragg Gratings

With the high integration of wet end,the optical fiber hydrophone array based on Fiber Bragg Gratings(FBG)has advantages such as high reliability,high sensitivity,and easy large-scale array formation.It has important applications in underwater detection,resource exploration,and other fields.Combined with software engineering technology,the research of the suppression methods of leading fiber noise(LFN)based on modulation and demodulation is carried out.The main research results are as follows:1.The LFN models caused by the polarization perturbation and Doppler effect are established,the corresponding numerical simulation is designed,and the characteristics of the two types of LFN are analyzed through engineering experiments.A comprehensive processing algorithm combining polarization switching(PS)and reference sensor is proposed,which can effectively suppress two types of LFN.2.The model of Rayleigh backscattering(RB)noise induced by the minimum common fiber(MCF)in interferometric FBG hydrophone is established,and the noise was characterized by engineering verification;A suppression method based on common phase modulation with the pseudo-random sequence is proposed,which can effectively suppress the RB noise.The main innovations are as follows:1.A comprehensive processing method for the polarization and Doppler noise is proposed,which effectively eliminates the influence of the intrinsic length and the birefringence disturbance on the leading fiber,and the noise suppression effect reaches39.7d B.2.The theory of MCF is proposed for FBG hydrophone array,and the pseudorandom sequence coding modulation method is innovatively introduced to effectively suppress RB phase noise.Experiments show that it can significantly reduce the RB parasitic interference intensity index,and the suppression ability is 21.3d B.The LFN is one of the bottlenecks restricting the application of FBG hydrophones to practical engineering.This thesis puts forward effective methods to suppress the LFN while maintaining the wet end simplified and integrated.The research can provide key technical support for the application of seabed vector arrays and light towed arrays based on interferometric FBG hydrophones.