利用光纤3层模型理论, 通过仿真研究发现长周期光纤光栅结构参数与透射谱的变化有规律性关系, 给出了一阶低次包层模与导模耦合时透射谱的变化规律。当长周期光纤光栅的纤芯、包层的半径和折射率增大时, 谐振波向短波方向漂移; 当长周期光纤光栅周期增大时, 谐振波向长波方向漂移; 当长周期光纤光栅长度增加时, 谐振波没有漂移现象, 但是其深度减小。通过综合分析发现: 谐振波漂移方向比较明确, 但是损耗峰深度的变化并没有明显的规律。

Based on the three-layer fiber model, we found that the relation between the structural parameters and the transmission spectra of LPFG is regular variation, and the variation rules of the transmission spectra were presented. This paper only considers the couple between lowest-order cladding modes and the fundamental core mode. When radii and refractive index of fiber core and cladding increase, the resonance wavelengths shift towards shorter wavelength; When grating period increase, the resonance wavelengths shift towards longer wavelength; When grating length increase, the resonance wavelengths have no shift, but its depth decreases. Comprehensive analysis shows that the shift in the resonance wavelengths is clear, but the change of depth doesn’t have distinct rules.