设计了一种准光子晶体光纤，其包层由呈准周期分布的空气孔构成，其中靠近芯区的空气孔的直径是渐变的。采用带有良匹配层(APML)吸收边界的全矢量频域有限差分(FDFD)方法对其色散特性进行了数值分析，计算了孔间距取1.5 μm～2.2 μm，最小空气孔直径分别取0.4 μm～0.6 μm，从第一层到第三层直径线性递增量分别为0.1 μm和0.2 μm的条件下，这种光纤基模的色散曲线。结果表明：通过调节包层中三种不同尺寸的空气孔的大小以及孔间距这四个参数，可以得到不同平坦水平的色散曲线，甚至于超低超平坦的色散曲线。例如，当孔间距取1.7 μm，空气孔直径分别取0.5 μm、0.7 μm 、0.9 μm，在1.4 μm～1.7 μm波段内，这种光纤的色散值可以控制在 6.0±3.0 ps/km.nm范围内。

In this paper, we design a photonic quasicrystal fiber with an air hole varying cladding. Its dispersion properties are analyzed by using the full vector finite-difference frequency-domain (FDFD) method with anisotropic perfect match layer (APML) absorbing boundaries. When the distance between adjacent air holes uaries from 1.5 μm to 2.2 μm, the least diameter changes from 0.4 μm to 0.6 μm and the diameter increases from the first ring to the third ring by a step of 0.1 μm and 0.2 μm respectively, its dispersion curves of the foundational mode are obtained. We find that the flattened dispersion at different levels, even the ultra-low and ultra-flattened dispersion curves can be obtained by adjusting diameter of three kinds of air hole in the cladding and the distance between adjacent air holes. For example, when the distance between adjacent air holes is 1.7 μm and diameters of air hole are 0.5 μm、0.7 μm and 0.9 μm respectively, the dispersion value can be controlled to 6.0±3.0 ps/km.nm in the wavelength range of 1.4 to 1.7 μm.