Optical secure communication system based on chaos synchronization

We propose a secure optical communication system based on the principles of generalized and complete synchronization of chaotic oscillations. Both a transmitter and a receiver are composed by two chaotic external-cavity semiconductor lasers which are coupled in a master-slave configuration to provide generalized synchronization, while the master lasers in the transmitter and in the receiver are completely synchronized via an optical fiber. A message is added to the slave laser in the transmitter and sent to the receiver to be compared with the output of the receiver slave laser. The system is robust to a small mismatch of the laser parameters or of the coupling between the master and slave lasers, unavoidable in a real system, and can even enable a good communication up to a 5 Gb/s transmission rate using the chaos masking encryption, when the master lasers in the transmitter and in the receiver are coupled bidirectionally.