Both channel coding and wavefront correction on the turbulence mitigation of optical communications using orbital angular momentum multiplexing

• We propose a turbulence mitigation scheme for optical communications using orbital angular momentum multiplexing based on both channel coding and wavefront correction.
• We use a Shack–Hartmann wavefront correction method to mitigate the phase distortion to reduce the crosstalk. We further use channel coding to correct the burst and random errors.
• We adopt the method using two static optical elements to convert the different helically phased OAM states to different lateral positions in the channel de-multiplexer.
• The scheme has a better mitigation effect than that using only wavefront correction method.
• The scheme has a better mitigation effect than that using only channel coding technique.

A free-space optical (FSO) communication link with multiplexed orbital angular momentum (OAM) modes has been demonstrated to largely enhance the system capacity without a corresponding increase in spectral bandwidth, but the performance of the link is unavoidably degraded by atmospheric turbulence (AT). In this paper, we propose a turbulence mitigation scheme to improve AT tolerance of the OAM-multiplexed FSO communication link using both channel coding and wavefront correction. In the scheme, we utilize a wavefront correction method to mitigate the phase distortion first, and then we use a channel code to further correct the errors in each OAM mode. The improvement of AT tolerance is discussed over the performance of the link with or without channel coding/wavefront correction. The results show that the bit error rate performance has been improved greatly. The detrimental effect of AT on the OAM-multiplexed FSO communication link could be removed by the proposed scheme even in the relatively strong turbulence regime, such as Cn2=3.6×10−14m−2/3.