A digital-controllable broadband analog optical chaos source is proposed. An analog-digital hybrid electro-optic feedback loop is introduced to enhance the robustness of the semiconductor laser based chaos system. The scheme could generate a broadband optical chaotic signal of high dynamical complexity. Robust digital synchronization strategies can be used for the proposed optical chaos sources. Compared with the existing schemes, the adoption of a semiconductor laser with self-feedback reduces the requirement on the processing speed of digital components. Meanwhile, the hybrid system structure could be simplified markedly. The proposed chaotic source has potential in long-haul secure fiber communication, chaotic radar, random number generation, and so on..
A secure scheme based on Rubik’s Cube (RC) transformation algorithm with low calculation complexity is proposed and experimentally demonstrated in the orthogonal frequency division multiplexing passive optical network system (OFDM-PONs). The RC transformation algorithm is adopted to generate encryption key stream for symbol substitution, and the chaos is utilized to control the RC transformation. An experiment with 7.64Gbps 16-quadratureamplitude- modulation (QAM) encrypted OFDM data are successfully transmitted over 25km standard signal mode fiber (SSMF). The experimental results indicate that the proposed scheme is an effective and promising method for physical-layer secure optical communication to meet the demands for low implementation complexity and high security performance.
A coupled system with varying parameters is proposed to improve the security of optoelectronic delayed feedback system. This system is coupled by two parameter-varied optoelectronic delayed feedback systems with chaotic modulation. Dynamics performance results show that this system has a higher complexity compared to the original one. Furthermore, this system can conceal the time delay effectively against the autocorrelation function and delayed mutual information method and can increase the dimension space of secure parameters to resist brute-force attack by introducing the digital chaotic systems.