Asymmetric channel gain and crosstalk in traveling wave optical amplifiers

Previous studies have shown that in multichannel optical amplification using a traveling wave amplifier, nonlinear frequency mixing effects can arise due to the modulation of the carrier density. It was shown that in the small-signal case, the carrier density modulation leads to a weak asymmetry in the gains experienced by individual channels. The authors extend the theoretical results by including the effects of gain saturation. They find, in the two-channel case, that the gain asymmetry can be as large as 10 dB depending on the channel separation, carrier lifetime, and input powers. The authors discuss the implications of this on the choice of modulation scheme