针对半导体激光二极管(LD)与单模尾纤(SMF)的耦合问题, 提出了一种基于渐变折射率光纤(GIF)的耦合机制。GIF被设计为SMF的前端耦合部分, 采用大芯径以匹配LD输出远场分布, 椭圆形的纤芯形状可有效匹配LD椭圆输出光束, 并实现有效聚焦与控制。基于有限差分束传播法对耦合过程进行的理论分析表明, 采用该方法功率耦合效率可达到88%, 1 dB插入损耗对应的GIF长度容差为75 μm,长轴与短轴方向的横向偏移容差分别为28 μm和10 μm。该方案对高功率LD耦合单模光纤设计有一定的参考价值。

The mechanism based on graded-index fiber (GIF) is provided for efficient coupling between laser diode (LD) and single mode fiber (SMF). As the central component, the GIF is placed in front of SMF. A large-sized elliptical core is designed in GIF for matching the far field of LD, and the beam from LD can be focused and coupled into SMF. By analyzing with finite difference beam propagation method, the power coupling efficiency is able to reach 88%. For 1 dB insert loss, the tolerance in fiber length of GIF is 75 μm, and the tolerances of offset in the direction of major axis and minor axis are 28 μm and 10 μm, respectively. The scheme is useful for the design of high power LD coupling single mode tail fiber.