Coding techniques for diversity enhancement of dense wavelength division multiplexing MIMO-FSO fault protection protocols systems over atmospheric turbulence channels

An enhanced transmission is presented in a multiple-input-multiple-output (MIMO) dense-wavelength division multiplexed (DWDM) free-space-optical (FSO) communication link using diversity coding techniques under the effect of turbulent weather phenomenon. The findings show good performance with an (8 channels × 2.5 Gbps data rate/channel) 20 Gbps 1500 m transmission distance. The bit-error-rate (BER), outage probability (OP), and signal-to-noise ratio (SNR) of the diversity combining techniques using maximum-ratio combining (MRC), selection combining (SC), and equal-gain combining (EGC) technique are evaluated in this work. The obtained results illustrate that Alamouti, space-time coding (STC), space-time block coding (STBC), space-time trellis code (STTC), orthogonal STBC (O-STBC), and quasi-orthogonal STBC (QO-STBC) on the minimum mean-square-error, and MRC are worth implementing on the DWDM-FSO wireless communication systems. The mitigation of atmospheric turbulence is achieved using MIMO diversity combining techniques coding. The simulation results for diversity coding techniques using QO-STBC/STTC and SC/MRC in the MIMO-DWDM FSO communication system can improve BER performance, OP, and SNR. The MRC exhibits the lowest OP and BER when compared with the SC and EGC. The numerical results demonstrate that the FSO communication link using DWDM QO-STBC/STTC improves the power penalty at both BER values under varying atmospheric turbulence conditions for ST, MT, and WT, in comparison to FSO systems without DWDM QO-STBC/STTC diversity coding techniques.