Phase-Transparent Amplification of 16 QAM Signals in a QD-SOA

We study the nonlinear phase distortions in a columnar quantum dot semiconductor optical amplifier (QD-SOA) for coherent 16 quadrature amplitude modulation (QAM) signals. A few ps gain recovery in the QD-SOA enables suppression of the pattern dependent phase noise, which is a major performance limiting issue in conventional SOAs. A 25 dB phase and intensity transparent amplification of 40 Gb/s 16 QAM signals is experimentally demonstrated by error vector magnitude measurement.