本文研究了以单轴晶体为内包层的双包层高双折射光纤的传输和偏振特性。在弱波导近似下，应用光波导理论，得出了O光与e光的色散方程及截止特性。通过计算机的模拟与分析，划分出了截止区、单模单偏振区、单模双偏振区及多模区；分析了单模单偏区和单模双偏区存在的条件；研究了单模双偏区两偏振模式的偏振色散特性。结果表明，几何参数S、光学参数Rx、Ry及外包层折射率n3对所划分的四个区域及所对应的偏振特性有着极为明显的影响。此结果为光纤保偏器的设计和应用高双折射单模光纤构成新型光纤传感器的设计提供了可靠的理论依据。

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。

建立了一光纤传感器系统，并对NO气体的特性进行了研究，得到了NO气体对光的吸收谱和光波长分别为350，400 及500nm 时，吸收特性随气体浓度变化特性。实验结果表明在一定条件下NO气体浓度与吸收百分比成线性关系。该系统的响应时间仅为5s，恢复时间在10s之内。

研究了三包层WⅠ和WⅡ型单模光纤的波导色散特性。结果发现在相同条件下，三包层WⅠ和WⅡ型单模光纤零色散点的调节范围比传统的双包层W型单模光纤明显增大。详细分析了几何参量P、Q和光学参量R1、R2对单模传输时的波导色散特性和低次模截止频率的影响。所得的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。计算波导色散的方法可推广到多包层光纤。

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。

A chirped fiber grating with cladding made of uniaxial crystal material whose optical axis is parallel to the axis of grating, i.e., z-axis is proposed. Electro-optic effect and elasto-optic effect in this kind of fiber gratings are theoretically analyzed for the first time. The influences of the electric field and the strain applied to the fiber grating cladding along z-axis on Bragg wavelength kB and the reflectivity spectra of this kind of chirped grating are theoretically examined using coupled-mode theory and transfer matrix method. The curves of Bragg wavelength kB as a function of an external electric field or the strain are theoretically obtained respectively for three kinds of uniaxial crystal materials as the grating claddings. The calculated results indicate that when the axial electric field applied to the grating cladding varies from 1

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.

fiber Bragg grating with cladding made of uniaxial crystal material whose optical axis is parallel to the axis of fiber Bragg grating was proposed. The ratio (Kcl) of the extraordinary to the ordinary ray refractive index was introduced and the influence of parameter Kcl upon the reflectivity γ, Bragg wavelength λB, the bandwidth of reflected wave △λ and the dispersion dq of this kind of fiber Bragg grating was examined using coupled-mode theory. The calculated results indicate that parameter Kcl has a strong impact on the characteristics of this kind of fiber Bragg grating, and the degrees of such impact are closely related to the values of parameter Kcl. This means Kcl can lead to the variation of Bragg wavelength while keeping its length, periodicity and the other parameters as constants. The fiber Bragg gratings using two kinds of uniaxial crystal material as cladding were discussed, respectively.

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.

The chirped Gaussian pulse broadening induced by chromatic dispersion in two kinds of tripleclad single-mode fibers with a depressed index inner cladding was examined in this paper. In view of the impossibility to deduce the expression of chromatic dispersion directly due to the complexity of the characteristic equations, a feasible approach to calculate chromatic dispersion was established, and the influences made by the optical parameters and geometric parameters on the chromatic dispersion and chirped Gaussian pulse broadening were analyzed. The calculated results indicated that the optical parameter, that symbolizes the third clad effect, has a strong impact on chromatic dispersion and pulse broadening, and the degrees of such impact were closely related to the other parameters and operating wavelength. The evolvement processes of a traveling chirped Gaussian pulse in the kinds of triple-clad single-mode fibers with different parameters were also analyzed