Determination of the origin of BER degradation utilizing asynchronous amplitude histograms

We propose a method that can determines the origin of BER degradation by analyzing amplitude histograms obtained by the asynchronous sampling technique. We measure asynchronous eye diagrams and evaluate both the waveform distortion caused by chromatic dispersion and the signal-to-noise ratio (SNR) deterioration by using electrical sampling to estimate the averaged Q-factor of 10 Gbit/s NRZ optical signals. Waveform distorted signals are shown to have histograms with different shape compared to signal-to-noise ratio degraded signals.