Amplifier-induced crosstalk in multichannel coherent lightwave systems.
01 January 1987
When an in-line semiconductor laser amplifier is used to amplify several channels simultaneously, it can induce interchannel crosstalk if the amplifier gain is channel dependent. It is shown that modulation of the carrier density at the beat frequency of two neighboring channels can lead to considerable crosstalk even when the amplifier is operated well below the saturation level. An analytic expression for the channel gains of a traveling- wave amplifier is used to discuss and compare the crosstalk for ASK and FSK systems. The relatively short carrier lifetime in high-gain amplifiers may ultimately limit the channel spacing of such multichannel systems.