Investigation of a Rate-Selectable All-Optical Packet Clock Recovery System

This letter presents the experimental performance of a rate-selectable all-optical packet clock extractor using a Fabry-Perot (F-P) filter, a semiconductor optical amplifier (SOA), and polarization interferometers (PIs). The F-P filter with a low finesse and a free-spectral range (FSR) equal to the lowest packet data rate was used to directly extract the packet clock from the packet data stream, which ensures that the clock locks fast and vanishes quickly. Different PIs, in conjunction with the F-P filter, were used to form comb filters with different FSRs in order to suppress the undesired subharmonic frequencies. The clock then goes into SOA to reduce the low-frequency amplitude noise. We demonstrate packet clock extraction at 10, 20, and 40 Gb/s with the combination filter.