长周期光纤光栅是在光纤纤芯中沿轴向形成折射率周期性调制的带阻型光纤器件。与光纤布拉格光栅不同 ,它表现为前向传播的纤芯基模与同向传播的各阶次包层模式在特定波长的耦合。研究了纤芯基模、包层模式(HE1l/EH1l)及其有效折射率随波长的变化 ,研究了纤芯基模与包层模式 (HE1l/EH1l)的耦合系数。研究表明 ,纤芯基模与一阶低次包层模式的有效折射率随波长增大而减小 ,纤芯基模与HE1l产生的耦合系数远大于与EH1l的耦合系数 ,并且包层模式次数较低时 ,耦合系数随次数的升高而增加。这与以前的研究结果有所不同。 Long-period fiber gratings are band-stop fiber devices that periodically modulate the index of refraction in the fiber core. In contrast to fiber Bragg gratings, it is characterized by the coupling of a forward-propagating core fundamental mode with a coherent propagating order-of-cladding mode at a specific wavelength. The fundamental mode, cladding mode (HE1l / EH1l) and effective refractive index of the core with the wavelength change were studied. The coupling coefficient between the core mode and cladding mode (HE1l / EH1l) was studied. The results show that the effective refractive index of the fundamental mode and the first order low cladding mode decrease with the increase of the wavelength. The coupling coefficient between the core mode and HE1l is much larger than the coupling coefficient with EH1l, and the number of cladding modes Lower, the coupling coefficient increases with the number of times. This is different from the previous study.