The upper bound is still the Shannon limit. The experiment does a lot of multiplexing: spatial multi-core fiber, spectral multi channel multiplexing across wavelength, dual polarization.

Each of the multiplexed channels are individually limited by the Shannon limit, and with higher power the fiber's Kerr effect creates interference which creates a sweet spot for the optimal optical launch power.

the novelty here is that the spectral channels are all generated from a single laser source rather than a laser per channel

It depends on what you mean by "possible", what future improvements you're considering, because otherwise the answer is just 1.84 Pbit/s.

But in very general, you have around 200THz of range for these infrared lasers. So on a single core, I'd expect the max to be within an order of magnitude of 200Tbps. They're using 37 cores, so they're getting 50Tbps per core right now.

Order of magnitude because it's not super hard to approach a bit per Hz of bandwidth from the bottom side, though difficult at very high frequencies, while it gets exponentially hard to exceed it. And here's a couple relevant charts for how fiber is extra self-limiting: https://i.stack.imgur.com/bwTy2.png http://opticalcloudinfra.com/wp-content/uploads/2017/07/Nonl...

>We also present a theoretical analysis that indicates that a single, chip-scale light source should be able to support 100 Pbit s–1 in massively parallel space-and-wavelength multiplexed data transmission systems.