Theory And Simulation Of Four Wave Mixing Noises In WDM Systems Based On CO-OFDM

In order to increase the capacity and spectral efficiency of optical communications and to cope with the explosive demand for data services,the Orthogonal Frequency Division Multiplexing(CO-OFDM)wavelength division multiplexing(WDM)system based on coherent detection is widely concerned.Such systems are important for implementing "Terabit Ethernet." Due to the relatively narrow sub-channel spacing and more sub-channel numbers in WDM CO-OFDM systems,the nonlinear effects,especially the four wave mixing(FWM),will affect such systems serio usly.Theoretical research and simulation to evaluate the impact of nonlinear effects on system performance is of great significance for the optimal design of such systems.In this paper,the theoretical and simulation studies on the nonlinearity of WDM CO-OFDM system are mainly focused on the cyclic prefix of OFDM,the dispersion management scheme and the polarization state of incident light.The specific work is as follows:1?This dissertation reviews the principles and advantages of OFDM and WDM,and describes the suppression of nonlinear effects by dispersion management.The comparison of OFDM and single-carrier system under different effects shows the advantages of OFDM and its nonlinear research.2?Because of the better performance of CO-OFDM system,the FWM is the main nonlinear effect.This paper mainly studies the influence of nonlinear effect based on FWM on CO-OFDM.The single-channel power pre-emphasis technique is compared with the WDM carrier wave filling algorithm.Simulation shows that the performance of WDM is superior,which lays the foundation for further research on WDM CO-OFDM system.3?Based on OptiSystem and Matlab,the WDM system of CO-OFDM is built,and the nonlinear separation model is used to control the addition of FWM noise.This paper simulates the effect of FWM on the system under cyclic prefix with different length,and finds out that the best value of its length is the maximum delay extension.The effect of FWM on the system and the non-linearity tolerance of the system are studied under different transmission rates,multiplexing intervals and number of channels,highlighting the advantages of new optical fiber links.In order to further study the role of polarization state,we built different dispersion compensation links on the original basis to study the influence of FWM based nonlinear effects on the system.