CO-OFDM DWDM系统非线性容限的仿真研究

Simulation Study of Nonlinear Tolerance in CO-OFDM DWDM System

为了提高光传输容量,提出了一种四进制正交幅度调制相干光检测正交频分复用系统与密集波分复用系统平行复用的超信道系统。利用Optisystem软件和Matlab软件搭建仿真平台,采用非线性分离模型控制四波混频噪声的加入,并使用误差向量幅度来测量误码率。在不同的传输速率、复用间隔和信道数下,通过仿真不同的循环前缀、入纤功率来研究四波混频对系统的影响和系统的非线性容限。仿真结果表明,随着循环前缀的增大,误码率先减小后增大,有最优取值,一般为快速傅里叶变换窗口长度的1/8。新型光纤链路超信道系统的误码率总是比常规光纤链路的小,且有更好的非线性容限。

In order to improve the optical transmission capacity,we present a super-channel system simulation platform based on Coherent Optical Orthogonal Frequency Division Multiplexing(CO-OFDM)system with 16 Quadrature Amplitude Modulation(16QAM)format and Dense Wavelength Division Multiplexing(DWDM).We use Optisystem software and Matlab software for co-simulation,and adopt the nonlinear separation model to control the addition of Four Wave Mixing(FWM)noise,and measure the Bit Error Rate(BER)by the Error Vector Magnitude(EVM).By considering the different Cyclic Prefixes(CP),combining multiplex intervals and channels,fiber power and other factor at different bit rates,we study the impact of FWM noise and the nonlinear tolerance of the system.The simulation results show that with the increase of CP,the BER decreases first and then increases.It is also shown that the optimal value of CP is the 1/8 of the Fast Fourier Transform(FFT)window length.For new fiber-optic links,the nonlinear tolerance is better than conventional fiber links.