Orbital angular momentum (OAM) modes routing in a ring fiber based directional coupler

Optical modes carrying orbital angular momentum (OAM) are becoming a hot topic, for that it promises a greatly improved information transmission capacity for fiber-optic communication systems. In this paper, we report our study on the coupling characteristics (coupling length and power transfer behavior) of OAM modes routing in a ring fiber based directional coupler. We decomposed an OAM mode propagating along a ring fiber coupler into its corresponding HE even and odd modes using beam propagation method. We found a general description of OAM modes in a ring fiber based coupler, which provides useful information for further study of fiber components using OAM modes.