Turbulence mitigation scheme using MMSE multiple-user detection for orbital angular momentum multiplexing communications

A free-space optical (FSO) communications with orbital angular momentum (OAM) multiplexing has largely enhanced the capacity, and atmospheric turbulence (AT) has caused a performance degradation for the system. Among the existed AT mitigation methods, the method with multiple-user detection (MUD) idea is shown to have used the AT interference as a useful component, instead of a noise, to the information detection. However, the random noise, except the AT interference, also has the bad effect on the system performance. In this paper, we propose a AT mitigation method based on Minimum mean square error (MMSE) Multiple-user Detection (MUD) method. The numerical simulation results show that MMSE MUD mitigation method can mitigate the effects of AT and random noise simultaneously. The performance of the OAM-multiplexed communications has been improved using the proposed AT mitigation method.