A 40-GHz 850-fs regeneratively FM mode-locked polarization-maintaining erbium fiber ring laser

An 850-fs pulse train at 40 GHz was directly generated from a regeneratively FM mode-locked fiber laser. The soliton effect was used to generate a short pulse and to suppress the supermode noise. The laser was locked to an external signal by a phase-locked loop (PLL) technique and the wavelength was tunable between 1540 and 1555 mn.