Numerical investigations of M-QAM chaotic optical communication with amplitude and phase encryption

We propose a M-QAM chaotic optical communication system under amplitude and phase encryption. In the legitimate transmitter (Alice), we first design an electro-optic nonlinear delay chaotic source which can provide chaotic optical intensity and phase carriers under ∼15GHz bandwidth. The M-QAM plaintext signal is masked by both chaotic optical intensity and phase carriers for ensuring the safety of intensity and phase information of M-QAM signal. In the legitimate receiver (Bob), the chaotic encrypted M-QAM signal after chromatic dispersion compensation by dispersion compensation fiber is decrypted by open-loop chaotic synchronization operation. Subsequently, the decrypted signal is processed by offline digital signal processing (DSP) module for impairments equalization. The proposed scheme is numerically demonstrated in an 84Gbit/s 8QAM chaotic optical communication system over 1100km standard single-mode fiber (SSMF), and a 112Gbit/s 16QAM chaotic optical communication system over 700km SSMF. We believe that the proposed scheme represents a promising strategy for enhancing the security of high-speed and long-haul optical communication system.