[lxgr]

Electromagnetic waves have perfect/lossless superposition, so radiation can’t really degrade a signal that way.

The big limiting factors are free space path loss and noise.

[Y_Y]

That's only true in classical electrodynamics, as it happens. If you're in a very strong B-field like you might find near a compact object you'll get nonlinear QED effects.

You can get a low order correction with Euler-Heisenberg: https://en.wikipedia.org/wiki/Euler%E2%80%93Heisenberg_Lagra...