Enhancing the Performance of Free-Space-Optics Transmission System Using Mode-Division-Multiplexing of Hermite–Gaussian and Laguerre–Gaussian Beams

Abstract

Emergence of 5G networks has led to rising demand for high-speed data networks. Free-space optics (FSO) play a pivotal role in providing high-speed large-capacity secure communication links required for fronthaul/backhaul services in 5G communication networks. Conventional FSO links are based on wavelength division multiplexing which make the system costlier, bulky and spectral-inefficient. In this work, a mode-division-multiplexing-(MDM)-enabled-FSO transmission system is proposed and evaluated to provide cost-effective, high-speed, and spectral-efficient data transmission. Hybrid Hermite–Gaussian (HG) and Laguerre–Gaussian (LG) modes are integrated to enhance the performance of the system. Four independent 10 Gbps data signals are transmitted along 2-distinct HG beams $\left({\mathrm{HG}}_{10}\text{and}{\mathrm{HG}}_{11}\right)$ and 2-distinct LG beams $\left({\mathrm{LG}}_{00}\text{and}{\mathrm{LG}}_{11}\right)$ over the free space channel. The performance evaluated is reported for clear climate and also for adverse rain climate where Quality factor metrics, Bit Error Rate Metrics, and eye diagram representation of the received signals are discussed. The proposed work reports definitive 40 Gbps along 11 km for clear climate followed by 1100–2300 m for varying levels of rain climate.