"Repeaters are included every 40-80 km to keep the signal strong."

Does it mean that there's a ton of repeaters under the sea? Where do they get the power from?

i believe they're simply powered by the electric conductors bundled with the cable

the extra interesting part i think is how they amplify the signal without having to decode it, just optically

https://en.wikipedia.org/wiki/Submarine_communications_cable...

They are like bulbs on an old-school Christmas tree light string, all in series with just one insulated conductor between.

Along the same cable. Data cables usually carry power to some degree too, for their own use.