Nonlinear Noise Model And Optimization Compensation Scheme In High-speed WDM Optical Transmission System

The combination of coherent optical communication and wavelength division multiplexing technology provides a potential solution to the increasing demand of bandwidth in Internet businesses,cloud computing and so on.As an effective method to improve the spectrum efficiency of digital coherent optical communication,the high order modulation format is also favored by many researches.However,when the system capacity is expanded by increasing the modulation order number and the signal transmission rate,the signal is more prominent by the fiber dispersion,the nonlinear effect and the noise deterioration.More accurate and efficient noise estimation and compensation methods are the challenges of the next generation communication system.Firstly,a 16QAM-WDM coherent optical communication simulation system has been constructed this paper.The nonlinear noise model in high-speed WDM optical transmission system is studied,mainly researching on the nonlinear noise generated by cross-phase modulation.The influence of polarization mode dispersion on nonlinear noise in PM-WDM system is considered,and the simplified estimation of nonlinear noise model is studied.This paper also focus on the compensation methods for phase noise.A new method,suitable for any phase compensation method of higher-order modulation format is proposed.The main research work is as follows:(1)A simplified nonlinear noise estimation model based on time domain signal of perturbation theory was proposed.Characteristics of the nonlinear noise and the validity of the estimated model are discussed in the simulation analysis with centralized or distributed amplification separately.Compared with the theoretical calculation results,the model proposed in this paper is able to estimate nonlinear noise accurately.(2)Considered the influence of polarization mode dispersion in PM-WDM systemi,the nonlinear noise estimation model proposed in this article is corrected.Besides,we verify the third-order nonlinear noise existgreat influence,which proves that the nonlinear noise correlation time can compensate by balancing technology.(3)A phase noise compensation algorithm based on local convex programming is proposed.The best search accuracy of this algorithm,hardware complexity and noise tolerance is analyzed.Compared with the current widely used algorithm in the simulation system,such as QPSK,blind phase search,secondary cascade with the maximum likelihood estimation method,we verify the complexity of this algorithm has the lowest hardware complexity and accurate compensation.