提出一种可用于宽带偏振无关光定向耦合器的新型双芯光子晶体光纤(PCF)，利用全矢量有限元方法分析了光纤结构参数对其光学特性的影响，得到了一组优化的双芯PCF结构参数,满足易于制作、易于接续和接续损耗低等应用要求,在此基础上对光纤结构进行了改进，进一步降低了制作难度，基于该光纤可以设计出在1.26~1.625 μm范围内分光比误差小于1%、两偏振态分光比误差小于0.2%的5050耦合器，并在现有实验条件下，试制了近似结构的双芯PCF。

A novel dual-core photonic crystal fiber (PCF) for broadband polarization-insensitive coupler with elliptical central hole is proposed. The impacts of its structural parameters on coupling characteristics are investigated in detail using full-vector finite element method. Optimizing fiber structure parameters, dual-core PCF is obtained and meets the application requirements of easy to fabricate, free to splice and low splice loss. Then an improved dual-core PCF is proposed for reducing the difficulty of fabrication. The coupler based on this fiber is obtained with the coupling ratio stabilized at (50±1)% and the coupling ratio difference between x polarization and y polarization less than 0.2% in wavelength range of 1.26~1.625 μm.