Accurate Q-factor estimation of optically amplified systems in the presence of waveform distortions

We present an accurate method for the Q-factor estimation even in the presence of waveform distortions in optically amplified systems. The method stands on the assumption that the dominant noises over the bit error rate (BER) are those superimposed on the nearest rails to the decision level. It is clarified that the assumption is usually satisfied. The results also show that, in numerical system evaluation, we should evaluate not only the eye opening but also the probability of occurrence of the rail level.