Abstract-We theoretically explored the system limits of various single-and multichannel transmission links employing semiconductor optical amplifiers (SOAs). For this purpose, we developed an accurate model to describe the amplifier dynamics in the moderate and low saturation regimes. Our simulation results revealed the delicate balance among the level of saturation, the signal-tonoise ratio, and the amount of gain per amplifier required for optimum system performance. The modeling results have been confirmed by recent experimental work in this area.Index Terms-Optical communication, semiconductor optical amplifiers (SOAs), wavelength division multiplexing (WDM).