Synchronization of chaotic diode lasers: application to data encryption

Abstract

An optical communication schemed based on chaotic encryption, that uses synchronised chaotic single-mode semiconductor lasers, is investigated theoretically. In this scheme the digital or analogic signal is encrypted by variable attenuation of the chaotic output of the transmitter. The masked message can then be decoded at the receiver using the the concept of synchronization of chaos. Optical feedback from an external reflector is used to induce chaotic behaviour in the laser diodes used in the transmitter and receiver. It will be shown that the chaotic behaviour of the receiver can be synchronised to that of the transmitter by injecting a small amount of the transmitter output into the receiver. Configuration based on both Edge-Emitting lasers and Vertical Cavity Surface Emitting Lasers (VCSEL) will be considered. The former will be modelled by a set of rate equations, while for the latter, the dynamics are analyzed using a travelling wave model which includes multiple reflections in the external cavity. It will be shown that under appropriate conditiosn an encrypted message can be recovered by properly manipulating the input and the outp of the receiver.