We report on jitter reduction and frequency tuning ability of 1.31 µm 40 GHz quantum-dot mode-locked lasers with the main focus on hybrid mode locking. The frequency of the external electrical source is usually chosen to be close to the passive frequency of the mode-locked laser, which is increasingly difficult for high frequencies far beyond 40 GHz.
Sub-harmonic mode locking is demonstrated, showing a significant jitter reduction down to 381 fs and a locking range of 6.6 MHz. 80 Gb/s on-off keying data transmission based on optical time-division multiplexing is demonstrated using a quantum-dot mode-locked laser module.