This work describes a simple and stable harmonically mode- locked erbium-doped fiber ring laser, that produces high power, ~ 1 ps transform-limited sech optical pulses. Pulse trains with different high repetition rates were obtained using harmonic mode-locking and rational harmonic mode- locking techniques. The temporal and spectral characteristics of the pulses are studied. The pulses are extremely appropriate for soliton based systems communications. Actively mode-locked erbium doped fiber ring lasers (MLEFL), have attracted much attention and are one of most promising candidates for soliton systems. This is due to some characteristics which are very convenient for high capacity optical systems: they can produce very short transform limited optical pulses at gigahertz rates. Such lasers also present high output powers, long term stability and can be easily tuned to operate in a wide region of wavelengths.