Secure Transmission of Optical DFT-S-OFDM Data Encrypted by Digital Chaos

This paper proposes and demonstrates a physical layer security-enhanced transmission scheme for discrete Fourier transform spread orthogonal frequency-division multiplexing (DFT-S-OFDM) signals in a passive optical network. During the DFT-S-OFDM transmission, the reconfigurable DFT matrix, the subcarrier allocation, and the training sequence for OFDM symbol synchronization are well encrypted by digital chaotic sequences generated via a 4-D hyperdigital chaos, which provides a huge key space of ~10 ⁴⁵ . Secure transmission of 13.3-Gb/s encrypted DFT-S-OFDM signals is demonstrated over a 20-km standard single-mode fiber, which proves the excellent confidentiality of the proposed secure DFT-S-OFDM transmission. Moreover, the receiver sensitivity is improved ~2 dB (BER@10 ^-3 ), which is due to the effective reduction of peak-to-average power ratio via DFT precoding. In addition, this scheme has the advantages of low computational complexity and has no requirement of redundant sideband information.