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。

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。

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

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.