In this paper starting from the ray path equations of a parabolic defocusing GRIN fiber lens with paraxial conditions, a equation to calculate the effective length of the fibre lens is derived.

• 从近轴条件下的光线轨迹方程出发,导出了计算抛物型发散梯度折射率纤维透镜有效长度的方程式,并讨论了该纤维透镜大端、小端对目标成像的孔径和视场。