A high power 320 Gbps CPDM-256-QAM based Ro-FSO system enabling 80 GHz under rain and haze effects

摘要

The proposed work presents a Radio over-Free space optical (Ro-FSO) communication system at 320 Gbps channel capacity using circular polarisation division multiplexed (CPDM) 256-Quadrature amplitude modulation (256-QAM). The proposal has been validated by comparing CPDM and LPDM in 320 Gbps 256-QAM Based Ro-FSO System enabling 80 GHz under Rain and Haze Effects. CPDM is a cutting-edge technology and has dominance over Linear PDM (LPDM) due to the elimination of polarisation axis alignment requirements and uniformity in the distribution of scattered light. In order to investigate the effects of CPDM and LPDM in Ro-FSO system, a performance comparison of both the PDMs has been accomplished for a range of Ro-FSO link lengths, and input powers under the effects of different atmospheric turbulences such as clear weather, haze, and rain in terms of Error vector magnitude (EVM), Quality factor (Q factor), and log Symbol error rate (SER). Further, the effects of Digital signal processing (DSP) in the proposed system are analysed using Viterbi Phase Estimation (VPE), Blind Phase Search (BPS), and Constant Modulus Algorithm (CMA) algorithms and it is observed that the presence of DSP tremendously improves the system performance due to mitigation of dispersion, nonlinear effects, time skews, and phase errors etc. Results revealed that under the clear weather, LPDM covered 28 km and CPDM managed to reach 38 km successfully. Power degrading effects in haze and rain are greater and therefore link length has been reduced to 5.5 km in CPDM and 4.9 km in LPDM for haze; and 4.2 km in CPDM and 3.8 km in LPDM for rain.