6G enabling FSO communication system employing integrated PDM-OAM-OCDMA transmission: impact of weather conditions inIndia.

Abstract

Currently, free space optics (FSO) transmission has gained attention due to its capability to deliver high data rates with a high level of security. In addition, using multiplexing techniques with FSO makes it capable of handling the excessive increase in traffic data and supporting the 5G and 6G wireless network requirements. Accordingly, in this paper, a novel, to the best of our knowledge, FSO system integrating three multiplexing techniques-orbital angular momentum (OAM) (four OAM beams are used) polarization-division multiplexing (two polarization states are used), and optical code division multiple access (four channels assigned with permutation vector codes are used)-is proposed. Additionally, the effects of rainy, foggy, dusty weather and the real weather for four different Indian cities that have different geographical locations are studied and investigated. The system performance is evaluated based on the bit error rate (BER), quality factor (Q-factor), maximum FSO range, and eye diagram opening. The simulation results show successful transmission of 320Gbps overall capacity with a maximum achievable FSO range of 7km under clear weather. On the other hand, the shortest FSO range of 0.105km is achieved when there are heavy dust storms. As for the Indian cities, Srinagar (hilly area of India) achieves the shortest FSO link, which is 4.2km while the largest range of 7km is observed for Chennai city (coastal area of India). All these ranges are evaluated for a log(BER) value <-7. Consequently, this proposed transmission model is suggested for use in 6G applications of FSO communication systems.