由于写入方式的限制,长周期光纤光栅（LPG）的实际折射率分布与经典理论有明显的差异,由此造成写入光栅的特性与经典理论的导出结果不能完全吻合。用傅里叶级数展开的方法对LPG逐点写入造成的高斯型折射率分布进行谐波分析,据此总结了高斯型折射率分布下光束形状与光栅周期的关系对谐波分布的影响,讨论了逐点写入的最佳参数选择,得出了对光栅写入和特性估计有关的结论,并给出了高斯光束逐点写入和振幅掩模板写入长周期光栅的透射谱比较。

Limited by the writing mode, the real refractive index distribution of the long period fiber grating (LPG) is different from that of the classic theory, which makes the spectrum of the real grating disagrees with ideal value. Fourier series is used to analyze the harmonics of Gaussian refractive index. Effect on the harmonics distribution caused by the relation between the beam size and grating constant is summarized, and the principle of optimum parameter selection is discussed. And some conclusions about LPG fabrication and character estimation are gotten. The transmission spectrum comparison between the long cyde grating written point by point with Gaussian beams and transmission by amplitude mask is obtained.