Secrecy Capacities of Optical CDMA Communication Systems Based on Gold Codes

Optical CDMA transmission systems can not only increase system capacity, but also achieve physical-layer security against fiber tapping attacks. In this paper, we examine the information-theoretic security of optical CDMA systems by evaluating the tradeoff between the achieved information capacity and the confidentiality. Moreover, we also evaluate the impacts of key system parameters, such as the number of users M, the number of stages of shift-register r (or code lengths L=2r-1) and the input optical power P, on the secrecy capacity and the interception probability. Our results indicate that key system parameters play an important role in enhancing the secrecy capacities, thus choosing suitable values of these system parameters will be helpful to improve the secure performance of optical CDMA systems to some degree.