Waveform distortion in a gain-saturated semiconductor optical amplifier for NRZ and Manchester formats

Waveform distortion due to gain saturation in a semiconductor optical amplifier (SOA) is studied numerically for different signal formats, NRZ and Manchester code. It is shown that the eye-opening penalty is nearly 0 dB for Manchester format sampled in the second half of one bit period while it increases with SOA input power or with signal bit rate for NRZ. It is also shown that extinction degradation for Manchester code is smaller than that for NRZ. These results are due to the fact that the signal level frequently changes between ON and OFF states and the pattern effect is small in Manchester format