A Study on 10-GHz Clock Signal Extraction from 160-Gbit/s RZ Optical Signals

A 10-GHz clock signal is successfully extracted from a 160-Gbit/s optical RZ signal using devices operable up to 40 GHz. The down-conversion of the 160-Gbit/s input signal into 40 Gbit/s signal is performed by modulating the input optical signal by an LN modulator that is driven by a RF signal with an amplitude of 3Vπ and a frequency of 40 GHz. Extraction of 10-GHz clock from the down-converted signal is done by an injection locking technique. An electrical PLL circuit is also examined for a reference. Regarding the recovered clock, basic properties of hold-in frequency range, frequency response, and phase jitter are found to be satisfactory. The faultlessness of the extracted clock signal was confirmed by bit error rate measurements.