Enabling 6G high spectral efficiency of PDM-OAM over FSOC channel model with weather condition effects in Iraq

This paper investigates a novel integration of hybrid polarization-division-multiplexing (PDM) with orbital-angular-momentum (OAM) multiplexing. Six user signals are multiplexing via a single-wavelength-spatial-laser. Our simulative system reveal 2 × 3 × 10 Gbps Gamma-Gamma fading channel based on NRZ encoding and 4-QAM modulation with 60 GHz RF carrier. Two-states of polarizations (X-PL and Y-PL) are introduced, each one has three Laguerre-Gaussian modes (LG₀₁, LG₀₂ and LG₁₁). 10 Gb/s data is carried per mode. The performance investigation is analyzed by varying free-space-optics-communication (FSOC) range under different weathers of Baghdad city in Iraq. The propagation length, eye-diagram, beam divergence and BER calculation are utilized as performance indicators. 60 Gb/s transmission is fulfilled along FSOC range with BER performance of 10^− 5, 10^− 7 and 10^− 6 in presence clear-air, rainfall and light dust, respectively. While the achievable transmission distances of clear atmospheric, rainfall and dust conditions are 800, 600 and 300 m, respectively.