Laser chaos generation, modulation and synchronization by electro-optical feedback in communication systems

Abstract

Chaotic dynamics are at the center of multiple studies to perfect encrypted communication systems. Indeed, the particular time evolution nature of chaotic signals constitutes the fundamentals of their application to secure the optical communications. The information coded on the carrier wave can be extracted with knowledge of the system dynamic evolution law. The work presents the implementation of experimental chaos generation systems by means of electro-optic feedback of the semiconductor laser. The output photocurrent of the optical receiver is amplified and reinjected as a feedback to the semiconductor laser source. The injected feedback photocurrent produces a chaotic behavior in the laser output. The change of the chaotic series and its jump from chaotic to periodic form depends on the initial operation condition of the laser diode and on the amplification of the injected feedback photocurrent. The chaotic signal has been used as a carrier for data transmission, the phase masking technique was used during the work. The data (message) signal was injected with the chaotic signal. Finally, two of the chaotic laser systems have been established to find the synchronization between two chaotic attractors. This step was done in order to extract the encoded message via the chaotic laser system.

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