Real-time secure optical OFDM transmission with chaotic data encryption

Offline digital signal processing is generally applied in secure optical orthogonal frequency division multiplexing (OFDM) transmission, however the real-time secure optical OFDM transmission is necessary to evaluate the security and transmission performances. Thus a real-time secure optical OFDM transmission with chaotic data encryption is developed to demonstrate the high-speed data transmission with high-level physical-layer confidentiality, where field-programmable gate array (FPGA) boards are employed for the real-time encryption and decryption of optical OFDM signals, along with pipeline analog-to-digital and digital-to-analog converters. The physical-layer security enhancement is attributed to hyper digital chaos, providing a huge key space of 1045. As a proof of concept, the real-time encrypted 16-QAM optical OFDM signal transmission at 435 Mb/s is successfully demonstrated over 22 km standard single-mode fiber (SSMF), without any degradation in transmission performance. The proposed FPGA prototype can be a good candidate for the practical implementation of secure data transmission in OFDM passive optical network.