Effect of a four-wave mixing on multichannel amplification in semiconductor laser amplifiers

A general theory is developed to describe multichannel amplification in semiconductor laser amplifiers. It includes the effects of both gain saturation and carrier-density modulation. The carrier-density modulation, occurring as a result of beating among the neighboring channels, is responsible for nondegenerate four-wave mixing. This nonlinear phenomenon not only unequalizes the channel gains but also generates new sidebands on both sides of the boundary channels. The effects of four-wave mixing on multichannel amplification are illustrated by considering the 30-channel case in detail. The theory is useful for quantifying the amplifier-induced crosstalk and identifying the operating conditions for reducing such crosstalk in multichannel coherent communication systems.<
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