I. Introduction

II. Overview of OWC

III. Contributions

IV. Principle of Free-Space Optical (FSO) Communication

V. Reliability of FSO Communication Systems

VI. Mitigation Techniques

VII. Radio over FSO (RoFSO) System

VIII. Multi-user FSO Communication

IX. MIMO FSO Systems

XI. Next Generation FSO Communication Networks

XIII. Research Challenges, Directions and Open Issues

XIV. Conclusions