Time- and Frequency-Domain Characterization of the Relative Intensity Noise of a Quantum-Dot Frequency Comb Source Laser

The intensity noise of a quantum dot, coherent comb source laser is characterized using time- and frequency-domain measurements. The time-domain measurements yield the average relative intensity noise (RIN) over the measurement bandwidth, and by calculation, the correlation time and power spectral density (frequency resolved RIN). The frequency-domain measurements yield the RIN spectrum and, by calculation, the integrated RIN. The short duration (50 mu s) time-domain results exhibit a line-to-line variability in the properties of the intensity noise that is not revealed by the frequency-domain measurements. It is shown that the RIN of a comb line can be reduced by over 13 dB using a saturated semiconductor optical amplifier (SOA). The performance of a low-complexity, low-latency 40 Gb/s intensity modulation, direct detection system using a comb line as a CW source, without and with SOA-based noise suppression, is assessed in terms of the bit error ratio.