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.