Analog–Digital Combined High-Secure Optical Communication System Based on Chaotic Circuit Driving

Abstract

We propose and demonstrate a new analog–digital combined high-secure optical communication system based on chaotic circuit driving, which achieves encryption in the analog and digital domains. A 3D chaotic system is used for analog domain phase encryption (ADPE) and digital domain time–frequency encryption (DDTFE) simultaneously. The ADPE is carried out by the privately chaotic signal driving the phase modulator (PM), which realizes chaotic phase encryption. The chaotic circuit comprehends highly complex nonlinear dynamics. Its size is 10 cm × 5 cm, which has the characteristics of small size and low cost. The DDTFE is performed by the frequency–time encryption of signals in the digital domain. The experimental results show that the optical physical layer encryption scheme based on analog and digital combination can successfully mask the original data. The driving signal of PM is that generated by the chaotic circuit and needs to be privately synchronized, so that the legal receiver may accurately decrypt the encrypted data and the eavesdropper is unable to intercept a valuable message. If the chaotic driving circuit produces a delay of 3 s, the bit error rate (BER) reaches more than 0.3 at the receiver. The results of experiment verify that the scheme can transmit 13.3 Gb/s 16 quadrature amplitude modulation orthogonal frequency division multiplexing (16QAM-OFDM) signal over 25 km standard single mode fiber (SSMF). This scheme achieves low-cost, high-security communication, making it a suitable foundation for high-speed, secure optical communication at the physical layer.