中文摘要：

相移光栅是构成DFB光纤激光器谐振腔的关键元件，当相移光栅制作中引入附加损耗时，耦合系数和光栅长度对DFB光纤激光器最佳输出特性会产生明显影响。采用传输矩阵法，数值分析了不同谐振腔损耗下最佳输出功率所对应的最佳光栅长度及耦合因子的变化。结果表明，在设计光纤激光器时，根据光纤光栅的制作损耗，优化光栅长度及耦合因子可以使光纤激光器的输出实现最佳化。这些结论对基于光纤激光器的结构优化具有指导意义。

英文摘要：

Phase-shift grating is a key component which forms the resonance cavity of DFB fiber laser. Due to additional loss, coupling coefficient and phase-shift grating length distinctly affect the optimum output power of DFB fiber laser. These factors were investigated by transfer matrix method. Through numerical simulation, the variation of the optimum output power with the optimum coupling coefficient and grating length under conditions of different cavity loss was analyzed. It shows that the optimal output power can be obtained by adjusting the optimum grating length and coupling coefficient according to the level of cavity loss. These conclusions can provide guidance for the optimized structure in designing the fiber laser.