Security-enhanced coherent optical chaotic secure communication based on linearly coupled reservoir computing

In this paper, we propose a security-enhanced coherent optical chaotic secure communication system based on linearly coupled reservoir computing (LCRC). LCRC scheme is used to replace the receiver in the conventional SLs-based chaotic secure communication system and enhance the anti-attack capability. Benefiting from the cross-prediction algorithm in reservoir computing (RC), the well-trained LCRC can achieve high-quality chaos synchronization with the transmitter, which can significantly reduce the system costs and challenges. Consequently, the normalized mean square error (NMSE) between the chaotic carriers predicted by LCRC and that from the transmitter reaches the order of magnitude of 10−5, the synchronization coefficient can reach 0.996, and BER of the 40 Gb/s 16 quadrature amplitude modulation (16-QAM) transmission signals via BtB scheme is much lower than the hard decision-forward error correction (HD-FEC) threshold of 3.8 × 10−3. Moreover, LCRC can still implement the chaotic prediction task without significantly degrading the communication performance even if one RC is destroyed due to the attack. Also, the impact of masking coefficient, SNR, and LCRC parameters on the prediction performance is analyzed in detail, and then the optimal parameter range is determined. Utilizing the interleaved encoding technology, 40 Gb/s 16-QAM messages can be successfully transmitted over 300 km fiber with BER of 3.56 × 10−3. In addition, higher-order QAM formats and different transmission rates have been verified feasible in our proposed security-enhanced LCRC-based communication system.