320 GHz time-domain multiplexed pulses from quantum-dash mode-locked semiconductor laser diodes

Quantum-dash (QDash) mode-locked (ML) Fabry-Pérot laser diodes have attracted significant interest in optical time-division multiplexing and wavelength-division multiplexing systems due to their variety of applications such as sub-picosecond pulse generation, frequency multiplication, multi-channel transmission, clock recovery, and clock generation [1–5]. In particular, clock generation has been demonstrated by using a programmable notch filter at the output of a 40 GHz QDash-ML laser [5]. Selection from two to three longitudinal modes at a given wavelength separation allows for the generation of sinusoidal clock signals at different repetition rates. In this work, an alternative approach based on optical time-domain multiplexing is experimentally investigated. Optical pulse-streams at 80, 160 and 320 GHz featuring optical signal-to-noise-ratios of 12, 9 and 6 dB, respectively, are obtained. Time-domain multiplexed pulses exhibit a full-width at half maximum (FWHM) of 1.8 ps irrespective of the pulse repetition rate.