利用有限元法对一种柚子型光子晶体光纤中的传输模式进行了模拟，得到了各传输模式的有效折射率和模场分布。结合耦合模理论和相关函数方法，对柚子型光子晶体光纤布拉格光栅反射谱进行了理论分析，解释了柚子型光纤光栅出现多个谐振峰的原因；数值分析了光纤纤芯直径和空气孔尺寸对光栅传输谱的影响。结果表明谐振峰波长随纤芯直径的增大向长波方向漂移，而随空气孔增大向短波方向移动，并且不同谐振模式的变化幅度不同；利用相位模板法写制了光子晶体光纤光栅，实验结果与理论分析能够很好地吻合。

The grapefruit photonic crystal fiber is simulated using finite element method (FEM). The effective refractive index and field distribution of each mode are calculated. Based on the coupled mode theory and correlation function mode-solver, the transmission spectrum of fiber Bragg gratings in grapefruit photonic crystal fibers is studied and the result explains the reason of multiple peaks. The influence of the structure change of the fiber core diameter and air hole size on the transmission spectrum is simulated. The results show that the resonance wavelength would shift to the longer wavelength with the increase of the diameter of the fiber core. The resonance wavelength would shift to the shorter wavelength with the increase of the size of the air holes, and the change is different for each resonant pattern. The fabrication of Bragg grating in a photonic crystal fiber is investigated experimentally by phase mask method. Experimental data are consistent with simulation numerical results.