针对经典-量子信号共纤同传的两种方案-同波段同传和较远波段同传, 分别推导了影响量子信号的主要噪声源-自发拉曼散射噪声计数率计算公式。在此基础上,分析了经典信号入射功率和传 输距离对量子密钥分发性能的影响。仿真结果表明：在同等经典信号入射功率条件下,同波段同传方案的自发拉曼散射噪声 计数率的数值大于较远波段同传方案；当经典信号入射功率上升时,同波段同传方案的自发拉曼散射噪声计数率随之上升的斜 率远大于较远波段同传方案；两种方案量子密钥分发性能同时受到经典信号入射功率和传输距离影响,当经典信号入射功率较大、 传输距离较近时,采用较远波段同传方案更合适,反之,当经典信号入射功率较小、传输距离较远时,同波段同传方案成为更优选择。

For the two schemes of classical-quantum signals simultaneous transmission sharing a same fiber-transmission in the same waveband and transmission in distant wavebands, the formulas for calculating the counting rate of spontaneous Raman scattering noise are derived respectively. Based on this, the influence of classical launch power and transmission distance on performance quantum key distribution is analyzed. The simulation results show that the counting rate of spontaneous Raman scattering noise in the same waveband is greater than that in distant wavebands under the same classical launch power. As the classical launch power increases, the slope of counting rate of spontaneous Raman scattering noise in the same waveband is much higher than that in distant wavebands. The quantum key distribution performance of the two schemes is affected both by the classical launch power and transmission distance. It ′ s more suitable to adopt the scheme of transmission in distant wavebands when the classical launch power is at high level and transmission distance is not so far. Conversely, it ′ s more suitable to adopt the scheme of transmission in the same waveband when the classical launch power signal is at low level and transmission distance is great.