在没有对喇曼增益分布做任何假设的情况下,利用所推导的光纤喇曼放大器噪声系数的解析表达式,研究了不同光纤长度、不同信号输入功率、不同增益、不同瑞利散射下双重瑞利散射导致的多路干涉噪声对喇曼放大器噪声系数的影响.结果表明随着光纤长度,信号输入功率、喇曼增益和瑞利散射的增加,多路干涉噪声对噪声系数的劣化越严重.但通过合理的优化光纤长度、控制喇曼增益可以取得噪声和增益间的最佳平衡.

A more accurate analytical expression for the noise figure of fiber Raman amplifiers is derived. Then the impact of multiple-path interference induced by double Rayleigh scattering on the noise figure of fiber Raman amplifiers is studied. The results show that impact will be more serious when the fiber length, input signal power and Raman gain are increased. But the results also show that if the fiber length is optimized and Raman gain is properly controlled one can achieve the best trade-off between the noise and Raman gain.