针对光子晶体光纤的非线性问题，设计了新型准光子晶体光纤结构。所设计的准光子晶体光纤的纤芯采用圆形空气孔，中心孔作为缺陷，前3层通过小孔结构形式实现内包层。结构的电磁场分析表明：随着入射角的增大，横向磁场模式的禁带会明显变窄，横向电场模式的禁带会明显变宽。参数分析后得出以下结论：在光通信的1 550 nm波长附近,结构的色散曲线表现了高平坦的特性；通过控制孔间距或者空气孔层数能实现限制损耗的控制，进而将损耗限制到非常小甚至为0的阶段。

In view of the nonlinearity problem in photonic crystal fiber, we design a new type structure of Photonic Quasi-crystal Fiber(PQF). The designed PQF has a circular air hole, where the center hole hasa defect.The first three layer structure is used to realize inner claddingthrough the holes. The electromagnetic field analysis shows that narrower forbidden band of TM mode and wider forbidden band of TE mode can be achieved by increasing the angle of incidence. Moreover, the parametric analysis indicates that at the wavelength of 1 550 nm in optical communication systems, flat dispersion characteristic is observed. Finally, the loss can be controlled at small value by adjusting the distance between the holes and number of air hole level.