All - Optical Clock Recovery Using Multi - SectionDistributed - Feedback

Recovering the frequency of an incoming data stream in optical transmission lines is important for signal processing. It has been suggested to use all-optical devices, for instance lasers diodes, for this purpose. If a self-pulsating laser is exposed to an external data signal, it is expected that the frequency of the self-pulsation locks to the frequency of the data signal, and clock recovery is realized. Such self-pulsations have recently been discovered experimentally in multi-section distributed-feedback lasers. Mathematically, it is then necessary to investigate frequency locking of periodic solutions, that is self-pulsating laser states, on invariant tori under external forcing which represents the external data stream. In this article, Melnikov functions are derived for periodic forcing, and results on frequency locking under aperiodic forcing are given. Using a model describing multi-section distributed-feedback lasers, the results are then compared with experiments.