The higher bit rates, lower noise figure, decreasing the nonlinear penalty of fiber system, longer amplifier length, tight channel spacing and operating near the zero-dispersion wavelength are achieved by using Distributed Raman amplifiers (DRAs). In this paper, a new model of noise figure (NF) due to amplified spontaneous emission (ASE) is introduced for the DRA at different pump schemes: co-pumping, counter-pumping and bidirectional pumping.

The variation of power conversion efficiency (PCE) with input pump power; input signal power and amplifier length for S-band is also investigated. It is found that, the NF increases exponentially with the fiber length and decreases exponentially with input signal power, power conversion efficiency (PCE) increases exponentially with the fiber length and input signal power and decreases exponentially with the input pump power. The obtained results show that, the noise figure (NF) reaches its minimum value of 8.6, 9.7 and 11 dB, while the PCE reaches its maximum value of 71%, 31% and 7% in counter-pumping, bidirectional pumping and co-pumping, respectively.

使用分布式拉曼放大器（DRA）可实现更高的比特率，更低的噪声系数，减少光纤系统的非线性损失，更长的放大器长度，紧密的通道间隔以及在零色散波长附近工作。本文介绍了在不同的泵浦方案（共泵浦，反向泵浦和双向泵浦）下针对DRA产生的由噪声放大自发辐射（ASE）引起的噪声系数（NF）新模型。

功率转换效率（PCE）随输入泵浦功率的变化；还研究了S波段的输入信号功率和放大器长度。可以发现，NF随光纤长度成指数增长，随输入信号功率成指数下降，功率转换效率（PCE）随光纤长度和输入信号功率成指数增长，而随输入泵浦功率成指数下降。获得的结果表明，在反向泵浦，双向泵浦和共泵浦中，噪声系数（NF）达到其最小值8.6、9.7和11 dB，而PCE达到其最大值71％，31％和7％。分别抽。