Fiber Nonlinearities in Short-Reach Systems: Modeling and Experimental Verification with 400G Digital Subcarrier Multiplexing

Modern metro and access optical networks, driven by 5G and fiber-to-the-home (FTTH), demand significantly higher capacity than current state-of-the-art direct-detection solutions can provide. Consequently, high-capacity coherent transceivers deployed, for example, in backbone and datacenter interconnects links, are now expanding into these new segments. However, unlike traditional long-haul links, the primary constraint in Passive Optical Networks (PONs) is the power budget. To ensure cost-effectiveness, efficiently scale the network, and reduce the need for in-line amplifiers, these systems may need to operate at elevated power levels to overcome distribution losses. However, this approach might increase the impact of fiber Kerr nonlinearities, which are typically negligible at lower launch power levels. This study addresses the resulting challenge of accurately modeling Nonlinear Interference (NLI) for short-reach links, which traditionally has been neglected. We validate a Monte-Carlo based Enhanced Gaussian Noise (EGN) model against Split-Step Fourier Method (SSFM) and the experimental measurements in 400G shortreach transmission links. The experimental results show a promising agreement (maximum deviation error <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\approx$</tex-math></inline-formula> 0.30 dB) with the EGN model. This work confirms the EGN model as a robust and reliable tool for designing also next-generation short-reach networks, enabling more efficient network design by accounting for the interplay between NLI and transceiver noise characteristics.