Maximum-Likelihood Optimal-Sampling-Phase Estimation for Ultra-High-Sensitivity Optically Preamplified Duobinary Receivers

We demonstrate a novel method for detecting optical duobinary signals. Oversampling in combination with maximum likelihood estimation based data processing of the O/E converted signal results in a record sensitivity for an optically pre-amplified receiver. The concept is investigated at 10Gb/s and allows data recovery at BERs of 1x10 sup -9 and 1x10 sup -3 with a receiver sensitivity of better than -39.5 dBm and an OSNR of only 7.8 dB, respectively.