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由于熔锥型光纤耦合器几何形状的特殊性,其耦合特性的研究通常是对于不同的区域采用不同的近似模型。构建了一个可以同时对耦合器各个区域耦合特性进行仿真的一致性模型。选取适当的连续函数描述锥形曲线和横截面形状;采用归一化的三角分布和高斯分布的加权叠加实现了模场沿耦合器各区域的连续变化。利用变分法和局部模式理论,推导出了耦合器任意位置处的耦合系数计算公式。该模型考虑了熔融区的纤芯效应,考虑了锥形区的耦合效应,是一个更为精细的理论模型。数值模拟结果显示,该模型可为光纤耦合器和波分复用器的制作提供理论指导。
Due to the particularity of the fused-tapered fiber optic coupler geometry, the study of its coupling characteristics is usually based on different approximation models for different regions. Constructed a consistent model that simulates the coupling characteristics of various regions of the coupler simultaneously. The conic curves and cross-sectional shapes were selected by the appropriate continuous functions. The continuous changes of the mode field along the coupler were achieved by the normalized trigonometric distribution and the weighted superposition of the Gaussian distribution. Using the variational method and the local mode theory, the coupling coefficient formula at any position of the coupler is deduced. The model considers the core effect in the melting zone and considers the coupling effect of the conical zone, which is a more elaborate theoretical model. The numerical simulation results show that the model can provide theoretical guidance for the fabrication of fiber coupler and wavelength division multiplexer.