Review on Performance Enhancement Techniques in FSO Systems

Free-Space Optical (FSO) communication offers a number of advantages like high capacity, low latency, and spectrum flexibility for backhaul and access links, which makes strong contender for acting as a key enabler for fifth-generation (5G) and beyond 5G communication networks. However, its extensive and large-scale deployment remains challenged by atmospheric turbulence, weather conditions, system complexity, and link reliability issues. This review presents a detailed study on FSO technologies and their possible application for next-generation communication applications. It discusses advanced concepts such as artificial intelligence and machine learning (AI/ML) for adaptive control of hybrid links, software-defined networking (SDN), and network function virtualization (NFV) for dynamic resource management, as well as an insight into unmanned-aerial vehicle/High altitude platforms (UAV/HAP)-assisted FSO links for extended coverage. The study also presents the energy-efficient architectures, quantum FSO systems, and reconfigurable intelligent surface (RIS)-based optimization approaches. In addition, the paper analyses the atmospheric impairments, tracking and security challenges, and major channel modelling techniques, highlighting the performance trade-offs in different turbulence conditions. A simulation study using Optisystem 22.1 compares the performance analysis using log-normal and Gamma–Gamma scintillation models under varying turbulence conditions, range performance, and Q-factor degradation. Finally, a comparative analysis of existing literature identifies the major achievements, limitations, and research gaps, offering a method for practical FSO deployment in 5G, B5G, and for 6G networks and guiding the development of future hybrid optical-wireless architectures.