CW injected, low-jitter, low-pedestal, gain-switched DFB-SLD/electroabsorption modulator-based pulse source at 1.5 μm for ultrafast network applications

Gain-switched DFB-SLDs are more susceptible to (uncorrelated) timing jitter than gain-switched Fabry-Perot SLDs. Continuous wave (CW) light injection was used previously to suppress the pulse timing jitter. Electroabsorption modulators (EAM) can be used to generate optical pulse trains from a CW optical source that can be readily synchronised to a network clock. The synthesis of the two methods, gain-switching and electroabsorption modulation, where the chirped pulses from a gain-switched DFB laser diode were temporally filtered with an EAM to reduce pulse width variation has been demonstrated. We report an extension of this method where CW light injection was used to reduce uncorrelated timing jitter and an EAM was used to suppress the pulse pedestal. The pulses that resulted had an uncorrelated root-mean-square timing jitter (URTJ) of 0.6 ps and a pedestal extinction of more than 25 dB