For anyone curious as to how they're actually laid, here's a simple diagram of a typical cable layer ship (CS):
http://www.murmanchanin.ru/shipnoise/polar_king/polar_king.j...
And a simplified diagram of how it operates:
http://www.murmanchanin.ru/shipnoise/polar_king/polar_king.j...
And a simplified diagram of how it operates:
The same thing with satellite launches. I feel like these are fairly major feats of engineering that go basically unheard of unless you're in certain small circles.
First, most EDFA (Erbium Doped Fiber Amplifiers) need power to operate since the lasers that perform the pumping action are local to the doped sections of fiber.
Second, most submarine cables make extensive use of Raman amplification which leverages the transmission fiber as a gain medium via forward or backward pumping of lasers with frequencies chosen to produce Raman gain.
In both cases, you need an amplifier every 70-100km (150km in some cases) in order to have a usable signal on a long span.
The power to run the lasers is usually carried on conductors that are part of the cable itself. The voltages are somewhere in the several kilovolt range so laying submarine cable is also kinda like laying a high-volage transmission line across the ocean.
A bunch of it was laid by ATT, which then got bought by Tyco.
The entry of that NJ HQ building was wild: It had pics of the ships used to maintain the cables. (When the cable needs to be pulled up in the middle of the atlantic, it's a bit of a challenge.)
IIRC, Tyco had 9 ships. If you glanced quickly, they looked like battleships with all the equipment on them. It was quite the operation.