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在使用窄线宽光源的干涉型光纤水听器远程传输系统中,瑞利散射通过多光束干涉引入了严重的相干噪声。分析了光纤远程传输产生的单次瑞利后向散射(RB)和双重瑞利散射(DRS)对干涉系统的影响,并使用隔离器对RB进行抑制。推导了DRS引入的相位噪声的模型,通过讨论DRS的调制特性,得出相位产生载波(PGC)技术在消除相位衰落的同时也可以大大抑制DRS产生相干噪声的结论。实验结果表明,在光纤水听器往返各25km的传输系统中,隔离器对RB产生的相位噪声抑制最大达20dB,PGC技术对DRS噪声的抑制最大达10dB。在同时抑制RB和DRS后,50km光纤传输系统中相干瑞利散射噪声的影响基本消除。
In interferometric fiber hydrophone remote transmission systems using narrow linewidth light sources, Rayleigh scattering introduces severe coherent noise through multi-beam interference. The influence of single Rayleigh backscatter (RB) and double Rayleigh scattering (DRS) on the interfering system caused by long-distance fiber transmission is analyzed, and the isolator is used to restrain the RB. The model of phase noise introduced by DRS is deduced. By discussing the modulation characteristics of DRS, it is concluded that phase - generated carrier (PGC) technique can greatly suppress the coherent noise generated by DRS while eliminating phase fading. The experimental results show that the isolator can suppress the phase noise of RB up to 20dB and the maximum of 10dB to the DRS noise in the transmission system with 25 km round-trip fiber optic hydrophone. After suppressing both RB and DRS, the influence of coherent Rayleigh scattering noise in 50km optical fiber transmission system is basically eliminated.