Spectral Properties of Quantum-Dots Mode-Locked Diode Lasers and the Impact in Fiber-Optic Systems

Coherent optical frequency comb based on single-section semiconductor quantum-dots mode-locked laser (QD-MLL) is a promising device, which is able to provide a large number of equally spaced spectral lines simultaneously. We discuss the measurements and the spectral properties of QD-MLL, including relative intensity noise, phase noise of each individual spectral line, as well as differential phase noise between spectral lines. More specifically, we report the frequency-dependent nature of QD-MLL phase noises, and its impact in the performance of coherent communication systems.