Spectral characteristics of optical pulse amplification in SOA under assist light injection

This paper analyzes the spectral characteristics of optical pulse amplification in semiconductor optical amplifiers (SOAs) with gain and transparent region assist light injection. It is shown that gain region light can decrease the spectral broadening and shifting, while transparent light cannot improve the spectral distortion, though it can accelerate the carrier recovery. The relationships of the frequency peak shift with the amplifier's bias current and length are also given; particular attention is paid to the differences between the co- and counterpropagating configurations.