4 GHz All-Optical Clock Recovery Using a Self-Pulsating Multielectrode Distributed Feedback Laser

Clock recovery is a major key function of any transmission systems. All-optical devices are very attractive due to their high speed and their simplicity as electro-optic conversion is not necessary. It has been shown experimentally that the self-pulsation (SP) in a multielectrode distributed feedback (DFB) laser can be synchronised to the data clock rate of an incoming optical return to zero (RZ) signal. This property makes SP lasers (SPL) good candidates for clock recovery in transmission systems. Jinno et al. [1] have shown a clock extraction at 200 Mbit/s and Barnsley et al. [2] at 5 Gbit/s. They both have used multielectrode SPL with one section operated as saturable absorber section, which limits SP frequency due to the limitation of carrier lifetime. Feiste et al. [3] have extracted 18 GHz clock by using a SP DFB laser without saturable absorber. We can note that in these experiments, the clock recovery occurs in injection locking conditions where the wavelength of the injected optical signal is nearly identical to the SPL wavelength. Despite the fact that such configuration allows optical carrier recovery with a few µW injected, it seriously limits the application of the SPL to clock recovery. This paper reports for the first time that a 3.8 GHz clock extraction with low time-jitter can be obtained even under conditions of large wavelength difference.