设计了一种改进的准光子晶体光纤, 其包层由呈准八重周期分布的空气孔构成, 其中靠近芯区的两层小空气孔的直径一致, 第三层以外的大空气孔直径一致。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1.40～2.50 μm, 小空气孔直径取0.10～0.50 μm, 大空气孔直径取0.20 ～1.00 μm的条件下这种光纤基模的色散曲线。结果表明, 通过调节包层中两种不同尺寸的空气孔的大小以及孔间距这三个参数, 可以得到不同水平的平坦色散曲线。

A modified photonic quasicrystal fiber is designed which has an octagon-fold symmetric quasicrystal array of air holes in the cladding. Small air-holes of the inner two rings and large air-holes of the outer rings in the cladding are adopted. The dispersion properties are analyzed by using the full vector finite-difference frequency-domain (FDFD) method with anisotropic perfect match layer (APML) absorbing boundaries. Its dispersion curve is calculated, when the distance between adjacent air holes is from 1.40 μm to 2.50 μm, the small air-hole diameter is from 0.10 μm to 0.50 μm and the large air-hole diameter is from 0.20 μm to 1.00 μm.The results show that the flattened dispersion at different levels can be obtained by adjusting the diameters of two kinds of air holes and the distance between adjacent holes in the cladding.