长周期光纤光栅包层模场分布及其耦合系数

基于简化的三层模型分析了单模光纤的包层模理论。研究了长周期光纤光栅的包层模块分布及其与基模的耦合系数。利用计算机建模，采用Ｍａｔｌａｂ对实用的ＳＭＦ－２８＾ＴＭ单模光纤进行模拟分析，得到了一阶不同次的层包模在沿光纤半径方向的光密度分布情况，及其与纤芯内的基模耦合系数的计算结果。证明了一阶低次奇、偶包层模在光纤纤芯内部的能量分布具有不同的特点，奇次包层模在纤芯内的能量远大于偶次包层模，因而奇次包层模

Cladding Mode Field Distribution and Coupling Coefficients in Long-Period Fiber Grating

On the base of simplified three layered model, this paper researched the theory of the cladding mode in single mode optical fiber, the cladding mode field distribution and the coupling coefficients of the cladding modes coupled with the core mode in long period fiber grating (LPG). With the aid of computer, Matlab was used to simulate the commercial SMF 28 TM single mode fiber, which found out the intensity distribution of the cladding modes in different orders of the first rank along the radium and the results of the coupling coefficients. It proves that the distribution of intensity in the core has different characters in the low odd and even orders of the first rank of cladding mode. The former is far more than the latter. Thus they have different coupling coefficients when coupled with the core mode. The former is also much bigger than the latter.