Suppression of supermode competitions in SOA fiber mode-locked ring laser

摘要

An actively harmonic model-locked fiber ring laser works at the modulation frequency which is the integral multiple of the fundamental cavity mode frequency spacing. As for harmonic mode-locking of erbium doped fiber laser, relaxation oscillation and beating between supernodes are the main noise sources introduced to the amplitude fluctuation and time jitter. (Here, the contribution to the instability due to the variation of the polarization is not considered.) However, a 10GHz actively mode-locked fiber ring laser with semiconductor optical amplifier (SOA) as gain medium is shown good amplitude stability compared with EDFA without the active cavity length stabilization, where no relaxation oscillation was observed and proved theoretically. In this paper, we will analysis the beating between supermodes in the mode-locked fiber ring laser and present the supermode competitions are suppressed due to the gain saturation in SOA and the shorter recovery time compared with EDFA.