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（16 QAM）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.