椭圆光纤基模偏振特性分析

提出光纤芯为椭圆型的光纤模型．通过高斯近似得出x方向和Y方向基模的相位差和光斑尺寸．提出两种偏振态表象在邦加球上的表达方式．利用邦加球分析了椭圆光纤内基模偏振态，得出离心率e，光纤芯长轴a，纤芯折射率ncn。和相对折射率差△不影响椭圆光纤中基模的偏振态．分析了椭圆光纤长轴a和离心率e对基模拍长的影响，结果表明拍长随离心率e的增加而迅速减小；拍长随光纤芯长轴a增加而迅速减小．进一步讨论了椭圆光纤芯折射ncn。和相对折射率差△对对基模拍长的影响，研究结果表明拍长随相对折射率差△的增加而迅速减小；拍长随椭圆光纤芯折射率ncn。增加而迅速减小．研究结果为设计偏振光纤提出理论依据．

Analysis on Polarized State of Fundamental Mode in Elliptical Fiber

A type of fiber with elliptical core is proposed. The fundamental mode of phase difference and spot size for the x - and y - direction is obtained by Gaussian approximation. Using Poincare sphere to analyze the polarized fundamental mode in elliptical fiber, it is obtained that eccentricity e, long axis in fiber a, refractive index in core nco and relative refractive index zi don＇ t exert influence on polarized state of fundamental mode in elliptical fiber. Analyzing influence made by long axis in fiber a and eccentricity e on beat - length of fundamental mode, it is shown that beat - length decreases with eccentricity e quickly ; beat - length decreases with long axis in core a. To deeply analyzing influence made by relative index in core nco and relative refractive index A on beat - length of fundamental mode, it is obvious that beat - length decreases with relative refractive index A ; beat - length decreases with relative index nco in core. It is also the theoretical foundation for designed the polarization fiber.