对单信道 4 0 Gbit/s归零码 (RZ)和非归零码 (NRZ)传输系统进行了实际模似。考虑了光纤损耗、二阶群速度色散、三阶群速度色散、偏振模色散及放大器噪声对系统影响 ,采用 Q值判别法计算了系统可传输的最大距离 ,绘出了系统眼图。计算结果表明 ,RZ的最大传输距离大于 NRZ码 ,RZ系统传输性能优于 NRZ系统 The actual simulations were performed on a single channel 40 Gbit / s return-to-zero (RZ) and non-return to zero (NRZ) transmission system. Considering the effects of fiber loss, second-order group velocity dispersion, third-order group velocity dispersion, polarization mode dispersion and amplifier noise on the system, the maximum distance that the system can transmit is calculated by Q value discrimination, and the eye diagram of the system is plotted. The calculation results show that the maximum transmission distance of RZ is greater than that of NRZ code, and the transmission performance of RZ system is better than that of NRZ system