On the basis of the OptiSystem platform

we present a nonlinear separation model for evaluating the impacts of FourWave-Mixing（FWM）noise on the system performance and also a novel dispersion map.By using this model

we simulate the FWM noise of the co-polarization Dense Wavelength Division Multiplexing（DWDM）systems with 33 channels.The simulation results show that under the given system conditions

apure Differential Phase-Shift Keying（DPSK）（i.e.all channels are DPSK modulated）system has better nonlinear tolerance than a hybrid DPSK and On-Off Keying（OOK）system.For novel dispersion management systems

with the increase of bit rate and incident optical power per channel

the impacts of FWM noise on the performance of the hybrid DPSK and OOK DWDM system are greater than those on the pure DPSK system.