低差分模式时延少模光纤的有限元分析及设计

Finite element analysis and design of few mode fiber with low differential mode delay

针对少模光纤展开研究,利用Comsol软件计算其模场分布、有效折射率,进而分析光纤的差分模式时延.通过分析不同结构参量对模式数量和差分模式时延的影响,设计出了两种低差分模式时延的少模光纤,即带有外下陷的渐变式光纤和多阶少模光纤.波长在1530-1570 nm范围内,带有外下陷的渐变式光纤支持四模传输,LP_(11),LP_(21),LP_(02)模式的差分模式时延的绝对值小于0.015 ps·m^(-1);多阶少模光纤支持两模传输,LP11的差分模式时延低于0.185 ps·m^(-1).两种少模光纤均具有良好的差分模式时延特性,适于在模分复用技术中应用.

Two different types of few mode fibers （FMFs） are considered： a graded-core with a cladding FMF and a multistep-index FMF. The characteristics of mode field distribution and the effective index are analyzed based on Comsol software. Then differential mode delay is analyzed. The structure and profile parameters are optimized in order to achieve the lowest possible differential mode delay （DMD）. Under the condition of supporting four modes, a graded-core with a cladding FMF is designed. The DMD absolute values of LP11, LP21, LP02 are all below 0.015 ps·m^-1. Under the condition of supporting two modes, a multi-step-index FMF is designed. The DMD of LP11 is 0.185 ps·m^-1. The designed fibers have low DMD, which is suitable for mode division multiplexing.