Experimental and theoretical studies of a high repetition rate fiber laser, mode-locked by external optical modulation

An experimental and theoretical study of a high repetition rate laser source operating on a novel mode-locking technique is presented. This technique relies on the fast saturation and recovery of a semiconductor optical amplifier induced by an external optical pulse and has been used to obtain 4.3 ps pulses at 20 GHz. A complete mathematical model of the fiber ring laser is presented describing the mode-locking process in the laser oscillator and providing solutions for the steady-state mode-locked pulse profile. The critical parameters of the system are defined and analyzed and their impact on the formation of the mode-locked pulses is examined. The comparison between the theoretical results and the experimental data reveals very good agreement and has allowed the optimization of the performance of the system in terms of its critical parameters.