【摘要】 本文给出了光纤中包层模的电场形式，指出包层膜的电场形式与弱导光纤中导模的电场形式不同，对光纤中基模与包层模电场沿光纤横截面分布的重叠情况的分析表明，长周期光纤光栅除了能将ＨＥ１１导模耦合到ＨＥ１ｐ包层模外，也可以将其耦合到ＥＨ１ｐ包层模．基于耦合模理论的计算表明，耦合到ＥＨ１ｐ和ＥＨ１，ｐ－１包层模的耦合波长相近，对于典型的单模光纤，当ｐ＞４时耦合到这两个模式的耦合系数是可比的．更多还原

【Abstract】 Electric fields of cladding modes in optical fiber are presented and it is pointed out that the electric fields of cladding modes are not as same as that of weakly guided modes.The analysis for the electric fields overlapping on cross section of fiber between the guided and cladding modes reveals that HE 11 guided mode can be coupled not only to HE 1p but also to EH 1p cladding modes by long period grating.Calculation basing on the coupled mode theory shows that couplings to HE 1p and EH 1,p-1 cladding modes are with similar wavelengths and when p>4 comparable coupling constants in a conventional single mode fiber.更多还原