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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场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-28TM单模光纤进行模拟分析,得到了一阶不同次的包层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,因而奇次包层模与基模的耦合系数远大于偶次包层模与基模的耦合系数
Based on the simplified three-layer model, the theory of cladding mode of single-mode optical fiber is analyzed. The distribution of mode field and the coupling coefficient with fundamental mode of long-period fiber grating are studied. By using computer modeling and Matlab, 28 TM single-mode fiber, the optical density distribution of first-order different cladding modes along the radius of the optical fiber and the calculation results of the coupling coefficient with the fundamental mode in the core are obtained. It is proved that the first- The energy distribution of odd and even cladding modes in the fiber core has different characteristics. The energy of the odd cladding mode in the core is much larger than that of the even cladding mode, so the coupling coefficient between the odd cladding mode and the fundamental mode Much larger than the coupling coefficient of the even cladding mode and the fundamental mode