Word-Synchronous Optical Sampling of Periodically Repeated OTDM Data Words for True Waveform Visualization

摘要: An improved phase-locked loop (PLL) for versatile synchronization of a sampling pulse train to an optical data stream is presented. It enables the true waveform repetitive high bit-rate time division multiplexed (OTDM) words such as pseudorandom bit sequences. Visualization can reveal details, which cause systematic errors. Such errors cannot be inferred from eye diagrams and require word-synchronous sampling. The programmable direct-digital-synthesis circuit used in our novel PLL approach allows flexible adaption virtually any problem-specific scenario, including those required sampling, jitter measurements by slope detection, classical eye-diagrams. Phase comparison performed at 10-GHz OTDM base clock rate, leading residual less than 70 fs.