光纤色散会使脉冲展宽，从而导致误码，在通信网中这是必须避免的一个问题。运用有限元法，在考虑石英基质材料色散的前提下，数值模拟了呈圆形排列的双包层光子晶体光纤的场分布、基模有效折射率和色散特性。结果表明，小空气孔间距和直径不变时，大空气孔与第一圈小孔的的间距和大空气孔的直径对色散曲线的走向起决定性作用。如同某些色散补偿光纤一样，有效模折射率会在某个波长处过渡，从而实现平坦色散，如当直径d1=3.1 μm，d2=1 μm，间距Λ1=5 μm，Λ2=4 μm时，在1.22～1.6 μm超宽波长范围内，其色散值Dmax-Dmin＜4 ps/(nm·km)。

Dispersion of fiber may broaden the pulse width and lead to error, which must be avoided in optical communications. Using the finite element method (FEM) and considering the material dispersion of SiO2, the mode field, the effective index of fundamental mode and the dispersion property of double-cladding photonic crystal fiber (PCF) with circular arrangement are numerically simulated. Results show that the distance between large air holes and small air holes of the first layer and the diameter of large air holes determine the shape of dispersion curve when the distance and diameter of small air holes are unchanged. As some dispersion-compensating fiber, the effctive mode refractive index has a transition at a wavelength,thus flattened dispersion can be realized. For example, when diameter d1=3.1 μm, d2=1 μm, distance Λ1=5 μm and Λ2=4 μm, within the wavelength range of 1.22~1.6 μm, the difference between the maximun and minimum of dispersion is less than 4 ps/(nm·km).