Optoelectronic phase-locked loop with balanced photodetection for clock recovery in high-speed optical time-division-multiplexed systems

An optoelectronic phase-locked loop (PLL) for clock recovery in high-speed optical time-division-multiplexed (OTDM) systems is proposed and experiment ally demonstrated. The proposed scheme incorporates a pair of balanced phot odetector through which the polarity ambiguity in error signal is resolved, and the cancellation of laser noise enables clock recovery with low timing jitter. Using an electroabsorption modulator as a phase detector, a 10-GHz clock signal with root-mean-square (rms) timing jitter of 300 fs is succes sfully extracted from 40 and 80 Gb/s return-to-zero (RZ) data stream. A 40- to 10-Gb/s demultiplexing is performed by using the recovered clock signal with no penalty introduced in the bit error rate performance.