Design and performance evaluation of MIMO-assisted coherent optical spatial diversity system under atmospheric impairments

Multiple-input multiple-output (MIMO) technology is an emerging scheme for achieving high speed and reliable communication by utilizing multiple channels for transmission and reception. MIMO diversity techniques are proven to be a promising solution to mitigate the effects of wireless channels such as propagation loss, atmospheric attenuation, turbulence, etc., by providing spatial diversity gain. This paper presents the design of a 2 × 2 diversity-assisted coherent MIMO free-space optical (FSO) communication system. The proposed system employs coherent 16 QAM transmitters and receivers and is evaluated under weak turbulence of FSO channels. System performance is analyzed using a constellation visualizer, eye diagrams, and received signal power under varying transmission distances and atmospheric attenuation conditions. The obtained results indicate that the MIMO configuration not only improves signal robustness but also resolves propagation-induced impairments. However, the second branch of FSO and Q-channel shows comparatively higher degradation of signals due to increased receiver sensitivity towards existing atmospheric turbulence and phase variations. Additionally, the proposed architecture maintains acceptable communication performance, making it reliable for high-capacity optical wireless hybrid networks.