利用硫系光子晶体光纤色散可控特性，设计了一种宽带超低色散平坦硫系光子晶体光纤，采用多极法研究了孔间距和占空比等参量对色散曲线的影响.通过优化包层中不同层数空气孔的直径，获得内两层气孔半径为0.7 μm，外两层气孔半径为0.8 μm和孔间距为5 μm的光子晶体光纤结构.模拟结果显示，该光纤在3~5 μm波段可实现宽带色散平坦，且色散绝对值低于3.8 ps·nm－1·km－1.

Using the dispersion controlled feature of chalcogenide photonic crystal fiber, the broadband ultralow dispersionflattened chalcogenide photonic crystal fibers was designed, and the multipole method was used to research the effects of the hole pitch and the aperture ratio on the dispersion curves. By optimizing the diameter of the air holes of different layers in cladding, the structure with 0.7 μm air hole radius of inside two layers, 0.8 μm air hole radius of outer two layers and 5 μm hole pitch were obtained. The simulation results show that this structure is broadband flattened dispersion in 3~5 μm, and the absolute value of dispersion is less than 3.8 ps·nm－1·km－1.