Noise characterization of a regeneratively mode-locked fiber ring laser

A regeneratively mode-locked fiber ring laser (RML-FRL) and an active harmonically mode-locked fiber ring laser (ML-FRL) have been characterized for both amplitude and phase noise by investigating the detected RF spectra of the optical pulse trains. Quantification of noise in the optical pulses reveals that the stability of the RML-FRL in terms of noise performance is superior to its ML-FRL counterpart. The optical pulse noise was measured over a frequency band of 100 Hz to 100 kHz and it was found that the pulse amplitude noise reduced from 0.6% in the ML-FRL to 0.3% in the RML-PRL. The total rms noise in the detected optical pulses from the RML-FRL improved by more than 30% compared to that measured for the ML-FRL, with a phase noise improvement of 15 dB at 100 kHz offset frequency from the carrier. An rms timing jitter of 0.38 ps was estimated in the optical pulse train from the ML-FRL, which reduced to 0.26 ps in the RML-FRL. In addition, complete elimination of the relaxation oscillations noise spikes in the detected RF spectrum of the optical pulses from the RML-FRL has been observed.