Performance Analysis of Delay Interferometer-based Scheme for Ultrafast Return-to-zero Data Pattern Effect Mitigation in Semiconductor Optical Amplifier

The feasibility of employing a delay interferometer (DI) to compensate for the pattern effect that manifests in a stand-alone semiconductor optical amplifier (SOA) when it is driven by return-to-zero (RZ) data being faster than its dynamic response is theoretically investigated and demonstrated. This is achieved by means of a numerical model applied to simulate and correlate the operation of these two elements in the context of their cascaded configuration. The outcome of this process allows to analyze and evaluate the impact of the input signal and SOA characteristics on the amplitude modulation of the sequence exiting each one of these devices. The obtained results disclose that owing to the utilization of the DI this quality metric is decreased compared to the case of a single SOA only while the technical limitations imposed on the involved critical parameters are significantly relaxed and their useful operational range is extended. These findings underscore the merit of placing a DI after a SOA for successfully combatting the undesirable pattern dependence and improving its performance when exploited purely for direct amplification purposes.