Bidirectional Chaos Communication Of Mutually Coupled Semiconductor Lasers In Series Connection

With the rapid development of optical network technology in recent years, the chaos communication system with high rate and high security has been studied frequently. Chaos synchronization and secure communication based on semiconductor lasers (SLs) have attracted much more attention because the chaotic carrier generated by SLs possesses some unique advantages such as wide bandwidth, high complexity, and easy to implement. There are many studies about chaos secure communication based on semiconductor lasers, much of which mainly investigate the chaos system of unidirectional coupled. Whereas, unidirectionally coupled system can not satisfy the needs of a great deal of communication. Bidirectional or multidirectional secret communications are always highly expected.In this paper, the theories of the chaos and chaos synchronization have been introduced, the chaos synchronization characteristics of mutually coupled semiconductor lasers are studied. Furthermore, bidirectional chaos communication between two outer semiconductor lasers coupled mutually with a central semiconductor laser are detailedly investigated. In this system, zero-lag high-quality synchronization between two outer semiconductor lasers can be obtained, while the cross-correlation coefficients between the two outer lasers and the central laser are very low under proper operation condition. Based on the high performance chaos synchronization between the two outer lasers, message bidirectional transmissions of bit rates up to 20 Gbit/s can be realized through adopting a novel decoding scheme which is different from that based on chaos pass filtering effect. Finally, the security of system is also analyzed for some possible attack scenarios, and the results indicate that the security of this scheme can be insured no matter which attack scenario is used by the eavesdropper.