Physical Encoding in Optical Layer Security

Data security at the physical layer of optical networks, or optical layer security, has received considerable research attention due to the rapid growth of optical network capacity [1]. Among various optical layer approaches, optical codedivision multiple access (OCDMA) systems are considered to be promising because of the physical encoding and decoding processes comprising these systems. Generally, physical encoding is an important concept in the field of optical layer security, which implements encoding to the transmitted optical signals, and protects the transmitted data from attack. In this paper, we provide an overview of various OCDMA systems, and discuss the impact of different physical encoding methods on OCDMA systems, in terms of security assurance. Furthermore, we introduce the application of physical encoding to optical steganography and optical transmission with wireless CDMA for security improvement.