Abstract: In recent year, technology development has taken place in communication standards such as fourth generation (4G) or fifth generation (5G) and we are experiencing a rapid growth in information and communication technologies. Moreover, the demand of higher data rates has been increasing with development in technology. Free Space Optic (FSO) connections are becoming an enchanting alternative for copper, RF and fiber optic communication techniques, in terms of speed, costing, distance and mobility. Higher data rate demands higher data security as well as reliability. Optical communication security is important not only at the management layer but also at the physical layer. The following article focuses on enhancements in FSO communication techniques to improve the reliability of the FSO link and data security. Line of Sight (LOS) is maintained using Fine Tracking System which uses 4-quadrant detector (4QD), the user data security can be achieved by implementing quantum cryptography, and a secure physical network can obtained by using Acousto-optic Deflectors (AOD).

Keywords: Acousto-optic deflector; Free space optic; Physical layer security; Data link layer security; User data security; quantum cryptography; Fine tracking system.