Dual-channel Chaos Synchronization And Communication Based On A VCSEL With Double Optical Feedback

With the rapid development of modern communication technology, a large number of scholars pay great interest on the study of a new generation of secure communication with high-speed, large capacity and excellent confidentiality. In recent years, the application of chaos synchronization in secure communication has received considerable attentions. Especially, with the development of the analysis technique for the delayed-time system, it is possible to obtain delay time of the external cavity from laser’s chaotic output to reconstruct the system, which will undoubtedly threaten the security of chaotic communication. As a microchip laser, VCSELs have more advantages than EELs, such as smaller size, oxide-aperture diameter and divergence, single longitudinal working mode and easier to coupling optical fiber and be integrated. Thus, VCSELs has wide potential application in the fields of optical communication, optical interconnects and optical storage. In addition, the output of VCSELs may have two orthogonal polarization modes, which makes it possible to realize the dual-channel synchronous communication between VCSELs.After taking two orthogonal polarization modes output from a VCSEL with double optical feedback as two chaotic carriers, a dual-channel chaos secure communication system has been proposed, and the frequency detuning between transmitting laser and receiving laser and injection strength impact system synchronization, the signal modulation and demodulation, the relationship between communication performance and information transfer rate, the synchronization and communication performances of such a system are numerically investigated. The results show that, under suitable operated condition, the time-delay signatures of two chaotic carriers originated by two linear polarization modes in the T-VCSEL with double optical feedback can be suppressed efficiently. Under strong injection locking case, high-quality chaos synchronization between two corresponding modes of T-VCSEL and R-VCSEL can be realized by polarization-preserved optical injection from T-VCSEL to R-VCSEL. Moreover, the tolerance of the synchronization quality on the frequency detuning between T-VCSEL and R-VCSEL will be enhanced with the increase of the injection strength. Adopting additive chaos modulation (ACM) encryption scheme, two500Mbit/s encoded messages can be hidden efficiently in the two chaotic carriers during the propagation process and can be successfully extracted at the receiver. Although Q factor will decrease with the increase of message transmission rate, the values of Q factor for two channels are still larger than6for6Gbit/s messages.