远程抽运光放大技术已广泛应用于超长跨距光传输系统。在介绍超长跨距光传输系统远程抽运光放大技术的设计方案基础上, 得出了远程增益单元的增益和噪声指数与远程抽运光放大系统输出光信噪比的关系。从选择掺铒光纤、采用反射镜和设计隔离器位置等三方面对远程增益单元(RGU)的结构设计进行了理论分析和实验研究，比较了不同方案下的远程增益单元的增益与噪声指数，通过优化光路设计，提出了不同抽运功率和信号光功率条件下的最佳远程增益单元光路结构。结果表明，选用低浓度的HE980掺铒光纤、采用高反射率和低插损的反射镜及设计合适的光隔离器位置，远程增益单元的增益和噪声指数能得到明显的改善。

Remote optically pumped amplification technology is widely used in ultra-long span optical transmission system. Based on designed scheme of remote pump technology of the ultra-long span optical transmission system, the relation between gain and noise figure with optical signal-to-noise ratio (OSNR) of system is obtained, the structure design of remote gain unit (RGU)from the choice of erbium-doped optical fiber, mirror used, isolator position design is theoretically analyzed and experimentally researched, comparing gain and noise figure of remote gain unit at different schemes. Through the optimization of optical design, the optimal optical structure of remote gain unit is proposed under the conditions of different pump powers and the signal powers. The results show that using low-concentration HE980 erbium-doped fiber, high-reflectivity and low-insertion loss mirror and suitable isolator position, the gain and noise figure of remote gain unit can be obviously improved.