围绕下一代光纤通信系统中轨道角动量(OAM)复用技术的关键问题，基于环状光纤中携带OAM的模式基础理论，仿真分析了环状光纤的不圆度对矢量合成OAM模式的本征奇模和偶模的有效折射率、走离长度以及模场强度分布的影响。结果表明，环状光纤不圆度会使得本征模式奇偶模之间的有效折射率差增大，走离长度减小，导致相应OAM模式在环状光纤中传输时稳定性下降。同时，不圆度的存在还会使矢量合成OAM模式的各本征模式的模场强度分布发生畸变，模场泄漏加剧。

In this paper, the key issues of Orbital Angular Momentum (OAM) multiplexing technologies in next generation optical communication systems is studied. Based on the theory of optical modes carrying OAM in a ring fiber, we study the influence of the ellipticity of the ring fiber on the effective refractive indices, walk-off length and model intensity profiles of the odd and even eigenmodes that form the basis of the OAM modes. Our results show that the effective refractive index difference between the odd and even modes of the same OAM mode increase with the ellipticity, thus reducing the stability of the corresponding OAM mode during propagation. Moreover, with the existence of ellipticity, the intensity profiles of the odd and even eigenmodes are distorted and the leakage of the mode field is intensified.