Digital-Twin of Physical-Layer as Enabler for Open and Disaggregated Optical Networks

The physical layer in optical networks is a set of transparent optical circuits — light-paths (LP)s — that has been extensively shown as reliably approximated by additive white and Gaussian noise channels. Noise sources setting the LP generalized SNR (GSNR) are the ASE noise from amplifiers, the nonlinear interference (NLI) from the Kerr effect and crosstalk from ROADMs. Coherent transceivers can be effectively modeled by the back-to-back characterization by defining the GSNR thresholds. We will describe the physics behind such approximation including the statistical impairments due the PMD, PDL and filtering penalties, and other uncertainties. Then, we will show how the physical layer digital twin (PHY-DT) that integrates the transmission impairment models can be exploited to reliably evaluate the QoT, latency and energy consumption on the topology. Finally, we will comment on the possible use of the PHY-DT as vendor neutral planning tool for disaggregated infrastructure and as on-line service within the multi-layer hierarchical controller. The optical devices controller can be separated from the optical circuit deployment, so enabling multi-vendor networks. We will also comment on the synergistic use of AI&ML techniques assisting the PHY-DT.