【摘要】 基于耦合模理论,提出一种判别圆双折射光纤的简易方法。首先指出在单模工作条件下的线双折射光纤中,一对互相正交的线偏振模间耦合系数为虚数,而在圆双折射光纤中,耦合系数为实数。从上述事实出发并根据单模光纤横截面上折射率分布的对称性,确定了光纤轴向倒置后几何形状不变是圆双折射光纤的三个必要条件之一。利用这种判别方法,可以确定对互易光纤而言,只有扭转圆光纤和熔融状态下制作的螺旋光纤才是真的圆双折射光纤。更多还原

【Abstract】 Based on the coupled-mode theory, a simple method to distinguish circular-birefringence fibers is presented. It is indicated that in a linear-birefringence single-mode fiber the coupling coefficient between two orthogonnal linearly polarized modes is a imaginary number, and the coupling coefficient will be real while in a circular-birefringence fiber. From this fact and the symmatry of the refractive index profile of the fiber crosssections, we conclude that fiber structure is kept unchanged in case of opposite location of fiber axes is one of the three necessary conditions for a circular birefringent fiber. According to this rule, only twisted fibers and helical fibers (drawn in viscous state at a high temperature) are really circular birefringent fibers.更多还原