They’re a composite cable, with fiber for the data portion and copper for the power needed to drive the fiber optic repeaters.

I was able to tour a fiber laying/maintenance ship back in the 1990s. Had it explained that they lay the cable powered and under end-to-end test (shore to ship). This makes the spool of cable into a giant electromagnet, meaning there were signs all over portions of the ship banning steel tools, watches, etc.

Yes. They are probably amplifiers not repeaters. The latter is now obsolete in long-haul transmission.