Rational harmonic mode locking of an optically triggered fiber laser incorporating a nonlinear optical loop modulator

Rational harmonic mode locking is first demonstrated in an erbium-doped fiber laser using an all-optical approach. Both bright and dark pulse trains up to 4.58 GHz are obtained at 1.55 μm by adjusting the initial reflection state of the intracavity loop mirror. The nonlinear loop modulator serves as a mode locker and an adjustable end reflector in the laser. The setup is useful for optional bit-rate multiplication while providing a means for the conversion of wavelength, as well as the conversion between bright and dark pulses. The output wavelength is also tunable upon the adjustment of a cavity fiber Fabry-Perot filter.