Investigation Of The Bidirectional Chaotic Security Communication Based On Fiber Channel

With the development of the informational society, the demands of the capacity and security of communication keep increasing. The new generation of technology with high speed and high degree of confidentiality has been a hot topic. Due to the sensitivities of initial conditions, high complexity, and long-term unpredictability, chaos is used to develop information secure technique at physical layer. Compared with electrical chaos, the optical chaos generated from the semiconductor lasers (SL) has attracted more attention in high speed and long distance secure communication because of its unique advantages such as broad bandwidth, low attenuation, high complexity and good compatibility with optical fiber networks. People have investigated the optical chaos synchronization and communication for near 20 years, but the investigation of the bidirectional and long distance fiber chaos security communication is insufficiency.In this paper, the theories of the chaos and chaos synchronization have been introduced, the influences of the optical fiber channel on the chaos synchronization and communication based on semiconductor lasers have been analyzed. Furthermore, a new type of bidirectional and long distance fiber chaos security communication system have been presented and investigated. Based on the chaotic synchronization of two response semiconductor lasers (RLs) under the injection from a common chaotic signal of a drive laser (DL), this new type of communication system permits bidirectional and long-distance information transmission in optic fiber channel. A corresponding theoretical model is established to study the bidirectional transmission performance and the system performance under different transmission distance. The results show that, when two RLs receive chaotic light injected from a the DL, the chaotic output of two RLs achieve a fairly good isochronal synchronization without any time delay, while there is a big difference between the signals of RLs and the signal of DL; if the ordinary single mode optical fiber (SMF) is used as a transmission channel, the Q factors of decoded messages can reach more than 6 after a propagation over 50Km; if the dispersion-shifted fiber (DSF) is employed, the Q factors of decoded messages can still reach more than 6 after a propagation over 200Km. In conclusion, this system can realize message bidirectional and long-distance security transmission in theory. Moreover, after analyzing the various ways which eavesdropper may obtain message, the system owns high security level.