Experimental validation of modified EGN model in real-time 400G/800G transmission with PCS and digital sub-carrier multiplexing

Abstract

An accurate and practical model of non-linear-interference noise (NLIN) is the key enabler for the quality of transmission (QoT) estimation tool, which predicts the penalty of transmission impairments. For next generation 400G/800G coherent transponders, probabilistic constellation shaping (PCS) and digital sub-carrier multiplexing (DSCM) are used to provide better transmission performance and finer data rate adaptability. However, to the best of our knowledge, there is little information so far about how to evaluate the penalty of NLIN in 400G/800G systems with PCS and DSCM, as traditional Gaussian noise (GN) or enhanced GN (EGN) model can not deal with such a problem directly. In this paper, we propose a modified EGN model to take into account the impact of PCS and DSCM on 400G/800G transmission system by performing simulations and experiments. To fully validate the accuracy of our model, a set of real-time experiments of 400G and 800G transmission system within 100/112.5GHz channel spacing, using 95GBaud commercial coherent modules. The 400G real-time transmission platform includes 10 spans of 75km G.652 fiber and all EDFA amplification is used, while the 800G link is limited to 5 spans G.652 fiber due to its higher OSNR requirement. The experiment result shows that the maximum estimation deviation of non-linearity induced OSNR penalty for the modified EGN model is about 0.3 dB under different transmission scenarios. We believe our work could potentially provide an effective and accurate tool for QoT estimation, paving the way for future physical-layer-aware management and control of high-capacity and flexible optical networks.