A Theoretical Analysis of Optical Clock Extraction Using a Self-Pulsating Laser Diode

The potential for using inexpensive compact disc laser diodes as optical clock extraction elements in transparent networks has led to an increase in research into the dynamics of self-pulsating laser diodes. We use a rate-equation model to simulate the synchronization of the self-pulsating laser output pulses to a periodic optical signal. In particular, we investigate the time it takes for the laser to synchronize to the input signal and also, the time taken for the laser to unlock when the signal is removed. The effect of varying the power of the optical signal and the detuning of the input signal frequency relative to the laser's self-pulsation frequency are determined. Our results enable us to identify important issues which need to be addressed when a self-pulsating laser diode is used in a clock extraction subsystem. In particular, we find that the signal frequency and laser free-running frequency must be as close as possible to minimize errors. Also, the higher the signal power the quicker the laser synchronizes to the signal, although we find that if the power becomes too large the laser can no longer lock, which would cause a significant increase in detection errors.