Polarization-Insensitive Clock Recovery Operation in a Monolithic Passively Mode-Locked Distributed-Bragg-Reflector Laser Integrated With a Tensile-Strained Multiple-Quantum-Well Saturable Absorber

A 40-GHz monolithic mode-locked laser diode integrated with a tensile-strained multiple-quantum-well saturable absorber was developed for the purpose of polarization-insensitive all-optical clock recovery in a single chip of a semiconductor device. Clock recovery with small polarization sensitivity less than 0.2 dB was successfully achieved. We also demonstrated a stable clock recovery from polarization-scrambled data signals.

Clock recovery/extraction is a fundamental function of signal detection and regeneration. All-optical clock recovery with a pulsating laser diode (LD) including a monolithic mode-locked LD (MLLD) [1]–[3] and a self-pulsation LD [4]–[8] is attractive to implement a compact, robust, and ultrafast clock recovery system with lower power consumption in large-capacity and long-distance optical communication systems. Recently all-optical clock recovery at beyond 100Gb/s of the operation speed has been successfully demonstrated in both the MLLD [2], [3] and the self-pulsation LD [8].