本文研究了一种双包层阶跃型光波导，内包层的折射率大于芯及外包层的折射率，因而可作为导波层。文中严格地推导了柱坐标下该光波导的特征方程，详细计算了TE波和TM波的传播常数、场分布及功率分布；作出了相应的曲线，表明了导波层的厚度、折射率及工作波长对此类光波导传播特性的影响。

Waveguide dispersion characteristics of two kinds of triple-clad single-mode (bers named WI and WII were examined in this paper. In view of the impossibility to deduce the expression of waveguide dispersion directly due to the complexity of the characteristic equations, a feasible approach to calculate waveguide dispersion was established. The calculated results indicate that the adjustable range of the zero-dispersion point of the triple-clad WI-and WII-type single-mode (bers is obviously wider than that of the conventional doubly clad W-type single-mode (bers in the same conditions. The in8uences made by the geometric parameters and optical parameters on the waveguide dispersion and cuto9 characteristics of low-order modes for WI-and WII-type (bers were analyzed. The method presented to calculate waveguide dispersion can be applied to multi-clad fibers.

Two kinds of the large effective-area fibers with the ring index profiles named RI and RII type were proposed. In view of the impossibility to deduce the expression of waveguide dispersion directly due to the complexity of the characteristic equations, a feasible approach to calculate waveguide dispersion was established successfully. The influences made by the geometric parameters and optical parameters on the waveguide dispersion and cutoff characteristics of low order modes were analyzed. The calculated results indicate that the dispersion-flattened and large effective-area performances can be achieved simultaneously by adjusting the geometric and optical parameters in a region of wavelengths. A dispersion-flattened fiber design with the total dispersion of about 4.5 ps/nm/km, dispersion slope of below 0.006 ps/nm2/km and the effective areas from 95 to 118 lm2 in the spectral range of 1540–1620 nm was presented and its tolerance analysis and bending loss characteristics at 1550 nm were also examined.

In this paper, the chromatic dispersion and chromatic dispersion slope of two kinds of triple-clad single-mode fibers with a depressed index inner cladding named WI-and WII-type were examined. A feasible approach to calculate chromatic dispersion and higher-order dispersion was established successfully, and the influences made by the optical parameters and geometric parameters on the chromatic dispersion coefficient and its slope were analyzed in detail. The calculated results show that the optical parameter R2; which symbolizes the third cladding effect, has a strong impact on the chromatic dispersion coefficient and the chromatic dispersion slope, and the degrees of such impact are closely related to the other parameters.

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。