A comprehensive survey of free-space optical communication – modulation schemes, advantages, challenges and mitigations

Abstract The demand for large bandwidth and high data rates in communication systems has become the main cause of the upgrade of traditional networks into free space optical (FSO) technology. FSO technology has gained significant popularity due to its easy deployment, high data rates, abundant bandwidth, enhanced security, and license-free spectrum utilization. However, the performance of FSO communication systems can be affected by certain limiting factors, such as changes in weather conditions during data transmission. To overcome these challenges and improve FSO performance, various modulation techniques are employed. This article presents a concise overview of the FSO communication system, highlighting different modulation techniques used to enhance its performance, as well as discussing its advantages, applications, and existing challenges. Some advanced modulation formats which are recently introduced in the field of FSO communication such as QPSK, DP-QPSK, QAM, and OFDM are also made part of this paper.