Amazon held their "re:Invent" event two weeks ago. Wasn't there, but
I'm a James Hamilton fan so I started watching the recordings of his
talks. In one, he talks about fiber optic cables under the oceans.
Here's the start of that section:
Even though this is presented at a suitable level for a large event
(32'000 attendees total, holy cow) of mostly non-network specialists, I
learned a few interesting things, e.g. about dealing with shunt faults.
If you rewind to a few minutes before that section, he also talks about
Amazon's private inter-DC network and how it is all (N*) 100G now.