Chaotic Multilevel Separated Encryption for Security Enhancement of OFDM-PON

A chaotic multilevel separated encryption (CMSE) scheme is proposed for physical layer security enhancement of orthogonal frequency division multiplexing passive optical network (OFDM-PON). In the proposed scheme, symbols in an OFDM signal are divided into several sub-matrices by matrix mapping and then encrypted by different algorithms selected from a set of alternative encryption algorithms based on 1D logistic chaotic systems separately. The signal processed by this scheme is encrypted at four levels. The four encryption levels depend on a matrix mapping rule, the specific algorithms, the order of used encryption algorithms and the key of each chaotic system. Any one of these conditions is essential for proper decryption. Compared with traditional methods, this scheme adds two new encryption levels and replaces the unique employed algorithm with multiple algorithms, which improves the security of system at the expense of a slightly increased complexity. An encrypted signal transmission of 22.06 Gb/s bit rate is successfully demonstrated over a back-to-back (BTB) system and a 25-km standard single mode fiber (SSMF). The experimental results prove that the CMSE scheme does not deteriorate the system performance and has good security against illegal attacks for future access networks.