A new feedback function to synchronize two diode lasers is introduced. This function is then applied to a secure communication system for decoding a message. Chaotic outputs of a direct-current-modulated long-wavelength semiconductor laser are used for encoding the message by direct amplitude modulation at the output of the transmitter. Numerical results show that the method of chaotic encoding is successfully employed in the cases of analogue and digital messages. Since long-wavelength semiconductor lasers are widely used for optical communication, this demonstration may prove to be useful for secure communication using chaotic optical systems. The message is decoded at the receiver by synchronizing it with the transmitter by the use of a proportional-integral feedback function, optimized for the case of semiconductor lasers.
V. Bindu and Dr. V . M. Nandakumaran, “Chaotic encryption using long-wavelength directly modulated semiconductor lasers”, Journal of Optics A: Pure and Applied Optics, vol. 4, p. 115, 2002.