On variable spectrum propagation in GNPy

[AndreaDAmico]

GNPy began as a planning tool for optical transmission simulations, providing an accurate estimation of the GSNR of a given lightpath as a performance metric in a worst-case scenario: the full C-band transmission scenario. In this way, the GSNR can serve as a conservative threshold for design and lightpath feasibility.
Numerous requests from the GNPy community, along with an increasing number of required practical applications in open and disaggregated optical network frameworks, have recently focused on the need for more flexibility in propagation scenarios, allowing variability of spectral load along the disaggregated network domains, enabling a more sofisticated and realistic digital model of optical transmission.
From this perspective, the following features must be implemented in the GNPy library:

1. The ROADM ability to add and drop channels to/from the propagated spectrum.
2. The EDFA must introduce a given GSNR penalty as a function of the spectral load percentage.
3. The creation of an additional layer to manage the routing and eventually the global current state of the network services load.

This is a memo for GNPy coders group but any suggestions are greatly appreciated. =)