On the Gaussian approximation and margin measurements in optical amplifier systems

By comparing with the exact optical communication system performance obtained using a quasi-analytical BER calculation method, we systematically analyze the accuracy of the Gaussian approximation (GA) method and the threshold-based margin measurement method for performance evaluation of on-off keying (OOK) optical amplifier systems. We reveal the inherent connection between the GA and the threshold method from both the one-shot case and systems with low inter-symbol interference (ISI). For systems with strong ISI, we show that GA method may fail but the threshold method still provides accurate system performance estimates, even when large threshold bias is used in the measurement.