各向异性内包层对双包层光纤特性影响的分析

提出了单轴各向异性材料为内包层，且其主轴沿光纤轴线（z轴）方向的双包层光纤模型，推出了矢量模特征方程，重点研究了主轴折射率比kcl对波导色散的影响，针对从矢量模特征方程求解波导色散因表达式极为复杂而无法直接求解的困难，提出了一种求解波导色散的有效方法，研究结果发现可以在不改变光波导结构参量的条件下，通过改变kcl可有效地改变光纤的波导色散，也分析了kcl、几何参量S、光学参量R对低次模的传输和截止特性的影响。研究结果为获得更为理想的色散补偿、色散平坦光纤及设计新型无源光器件提供了重要的依据。

Analysis of Characteristics of Doubly Clad Fibers Influenced by Birefringent Single Crystal Cladding

A doubly clad optical fiber with an inner cladding made of birefringent single crystal whose optical axis is parallel to the fiber axis is discussed. Exact characteristic equations are derived for vector modes. The influence of the ratio ( k cl ) of the ordinary ray refractive index to the extraordinary ray index upon the waveguide dispersion is analyzed in detail. It is impossible to deduce the expression of waveguide dispersion because of the complexity of the characteristic equations, a feasible approach to calculate the waveguide dispersion is presented. The results show that with the change of k cl , the value of waveguide dispersion changes correspondly as the geometrical and optical parameters (S and R) keeping invariable. The influences made by k cl , S and R on the propagation and cutoff characteristics of low order modes are also analysed. The result provide a significant reference for designs of new types of dispersion flattened fiber, dispersion shift fiber and passive optical devices.