Study On Digital Back-propagation Algorithm And Ring-based WDM-PON With Rayleigh Backscattering Noise Mitigation

With the development of optical fiber communication technology,fiber nonlinearity becomes a main limit to the capacity of optical fiber communication system.Many nonlinear compensation schemes have been proposed,among them,DBP,which takes advantage of DSP technology,can effectively compensating fiber dispersion and nonlinear effect in digital domain and is becoming a hot area of research.In addition,in order to satisfy the demand of bandwidth in access network,WDM-PON has been considered as a promising technology.However,RB noise may severely impact the performance of WDM-PON system,it is very important to mitigate RB noise in WDM-PON system.DBP depends on the parameters of fiber link,however,the parameters in dynamic network cannot be determined.A-DBP algorithm can adaptively compensating nonlinear effect,but the high computational complexity is an obstacle.In this dissertation,a modified A-DBP based on the intensity information of signal is proposed,partitioning and remapping technique is introduced to determine nonlinear coefficient,and quadratic interpolation method is introduced to realize the iteration of the algorithm.A 25 GBd dual-polarization 16-QAM coherent optical communication system with a distance of 2000 km is established by using simulation software,the performance of the proposed A-DBP and previous algorithms are compared.It is proved that the proposed A-DBP algorithm can have better performance,and the computational complexity of the algorithm can be reduced.In order to mitigation RB noise,a scheme based on orthogonal coding is proposed in this dissertation,and it is used to mitigate the RB noise in ring-based WDM-PON,the cost can be reduced.The orthogonal coding RB noise mitigation scheme in ring-based WDM-PON is verified in experiment.The experiment results show thatthe proposed orthogonal coding scheme can improve the performance of upstream transmission.When the data rate of downstream siginal and upstream signal are respectively 5Gb/s and 2.5Gb/s,the proposed orthogonal coding scheme can have a power margin of 1.8dB.And when the data rate of downstream siginal and upstream signal are both 5Gb/s,the power margin of the proposed orthogonal coding scheme can be up to 1.69 dB.