All-optical clock recovery using multisection distributed-feedback lasers

Recovering the frequency of an incoming data stream in optical transmission lines is important for signal processing. It has been suggested that all-optical devices, for instance lasers diodes, be used 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 multisection 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 that 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 multisection distributed-feedback lasers, we then compare the results with experiments.