Point-to-multipoint and ring network communication based on chaotic semiconductor lasers with optical feedback.

In this paper, two configurations of point-to-multipoint (PTM) and ring networks, based on the chaotic semiconductor laser subject to optical feedback, are investigated. A bifurcation diagram and the maximum Lyapunov exponent in the system have been used to distinguish the existence of chaos, and the complex degree of chaotic output is measured through Lempel-Ziv complexity. These results show that feedback strength has a significant effect on the dynamics of the system, namely, an increase in it can induce the system to enter into chaos. In the PTM model, it can be seen that the arbitrary receiver laser (RL) and central transmitter laser (TL) are identically synchronized, and moreover, the synchronization solutions are robust; the message can be encoded by modulating the bias current of the central TL, and at each RL end, the message from TL can be simultaneously recovered by monitoring the power error between RL and TL. As a result, the unidirectional broadcast message transmission, based on PTM, can be well achieved. In the ring network configuration, the coupling between two adjacent lasers through a partially transparent mirror induces the delay and chaotic dynamics. We prove that the dynamics is identically synchronized, and the synchronization against external perturbation also possesses good robustness; the messages introduced on the two arbitrary lasers in this ring network can be simultaneously exchanged.