Multi-Gbit/s real-time modems for chaotic optical OFDM data encryption and decryption

Real-time high-speed modems are proposed and demonstrated for physical-layer secure encryption and decryption of optical orthogonal frequency division multiplexing (OFDM) signals using field programmable gate array (FPGA). In the modems, the multi-fold data encryption is applied, including chaotic XOR, chaotic permutation and chaotic dynamic mapping, to enhance the physical-layer security for optical OFDM data during transmission. Real-time modems for encrypted 16-QAM OFDM signals at 4.8 Gbit/s are successfully demonstrated, using parallel multiple channels design on FPGA. The security performances of the real-time encrypted OFDM signals are evaluated, while a huge key space of ∼10168 is created to resist the exhaustive attacks.