通过对光纤光栅折射率调制进行傅里叶变换,推导出适用于非均匀栅格分布和调制深度的耦合模方程。从频谱分析的角度,提出一种适用于分析非均匀超长周期光纤光栅(ULPFG)的新方法,新方法指出非均匀超长周期光纤光栅可以等效为不同周期光栅效果的叠加。经数值模拟和实验刻制对照表明,这种基于频谱的分析方法在分析光栅栅格数、啁啾大小等因素对光纤光栅频谱的影响以及光谱中某一位置对应多个谐振峰的现象具有明显的优势。 Through the Fourier transform of the FBG’s refractive index modulation, a coupled-mode equation suitable for non-uniform grid distribution and modulation depth is derived. From the perspective of spectrum analysis, a new method suitable for the analysis of non-uniform ultra-long periodic fiber gratings (ULPFGs) is proposed. The new method indicates that non-uniform long-period fiber gratings can be equivalent to superposition of different periodic grating effects. Comparisons between the numerical simulations and experiments show that the spectral-based analysis method has obvious effects on the spectrum of the fiber grating and the resonance peaks corresponding to a certain position in the spectrum when analyzing the number of grating grids and the chirp size The advantages.