Research And Application On The Stochastic Distributed Scattering In Optical Fiber Transmission System

The stochastic scattering in optical fiber,including the Rayleigh scattering,the Brillouin scattering,and the Raman scattering,is of great significance in the optical fiber transmission systems.With the extensions on the application of the fiber stochastic scattering,the temporal randomness,the spatial randomness,and interactions among the stochastic scatterings.have obvious impacts on the fiber transmission system.In the optical amplifiers,the optical link monitors and the optical sensors,the system performance depends on the random variations of the scatterings with time and locations.Especially,in the long-reach fiber transmission system,since the high total optical launch power,the interactions among the Rayleigh,Brillouin,and Raman scatterings are extremely intense to induce other fiber nonlinear effects.The conventional theories of the fiber stochastic scatterings were confronted with some problems.On the one hand,the conventional theories were insufficient to deal with the randomness of the scattering,since the theories did not take the spatial randomness of the scattering sources into account.On the other hand,the conventional theories neglected the interactions among different stochastic scatterings.However,the interactions between the Rayleigh and Brillouin scattering has a significant effect on the performance of optical timedomain reflectometry(OTDR)with high dynamic range,and the noise characteristics in the fiber Raman amplifiers depended on the interaction between the Rayleigh and Raman scattering.Therefore,the conventional theories of the fiber stochastic scatterings could not precisely analyze the phenomena in the novel fiber transmission systems and limited the developments of the fiber systems.In this thesis,we firstly experimentally studied the problems induced by stochastic scatterings in the fiber transmission systems.Then,we built the novel theoretical models aiming at the temporal randomness,the spatial randomness,and interactions among the stochastic scatterings.Our proposed models could more preciously analyze the characteristics of the stochastic scatterings and the performance of the fiber transmission system.The main researches and innovations are summarized below:(1)For the short-reach optical fiber communication system,we built the model of the interaction between the backscattering and the signal lights and analyzed the characteristics of the backscattering noise in time and frequency domains.According to the model,we investigated the influence and mitigation of the Rayleigh backscattering in the bidirectional passive optical network(PON)with colorless optical network units.(2)For fiber link monitoring and sensing systems,based on the Shannon limitation theory,we analyzed the limitation between the spatial resolution and the dynamic range in OTDR.Then,we proposed a kind of OTDR employed the linear frequency modulation,fractional Fourier transform,and electrical frequency-division multiplexing.We also modified the theoretical model of the Rayleigh and Brillouin scatterings,which can be used for the analysis of OTDR,phase-sensitive OTDR and Brillouin OTDR.(3)For the long-reach optical fiber communication system with distributed Raman amplifiers,we proposed the models of the stochastic scattering noise spectrum and the optical field transmission to deal with the interactions among the Rayleigh scattering,spontaneous and stimulated Raman scatterings simultaneously.The noise spectrum model can be used to calculate the optical signal to noise ratio for evaluating the performance of the fiber communication system.Employing the optical field transmission model,we could obtain the characteristics of the Raman system under the influences of fiber attenuation,dispersion,Raman gain,nonlinear effects and the interaction of signal and noise.The two models are with significance for the performance assessment of the optical fiber communication system with distributed Raman amplifiers.