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Comment by lordnacho | Hacker News Reader

Happens quite often to subsea cables. I was renting a number of them and every now and again you'd get a break. You can follow the NOC's update emails:

Break detected

Ship has been commissioned

Ship is at harbor

Ship has sailed out to the cut

Fusing the ends

Service restored

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What's the typical timeline for that cycle? Hours, days, weeks? Just curious. I'm sure it costs an astronomical amount of money.

Days, but I had one time where the ships were booked up and it took longer.

What's the kind of scenario where you'd be renting an undersea cable?

Servers in different financial exchanges that need to talk to each other, reasonably fast.

How the hell do you fuse the ends of a massive cable like this at the bottom of the sea?!

You pull it up to the surface and fuse it on the boat.

Find it, pick it up, patch it on deck, lower it back down.

You find the ends, pick them up, and there's a kit that can fuse the ends to your new piece. I'm not sure about the details, but I think there are repeaters on the wire that need to be added as well.

A repeater on the ocean floor? Do they run power cables to it alongside the data all the way from the coast?

Yes, commonly there are high-voltage cables in there.

Nowadays, for shorter runs (that are still long enough to need repeaters) there are also purely optical repeaters where instead separate fiber strands deliver light from a pump laser.

Do they just fuse any strand to any strand and resort everything at the end or?

Strands in a bundle would likely have color coded sheaths. As long as you're not colorblind, it's pretty straightforward matching what gets spliced where.

For submarine cables, there aren't that many strands, so getting it right is probably worth it, for terrestrial fiber, there may be 100+ strands, so they usually can sort things out at the ends, and I think you just fuse any strand to any strand. Sometimes, only some strands break and you can reallocate strands by priority until the cable can be fixed.

This has pretty good information on it, and a couple videos:

https://www.onesteppower.com/post/subsea-cable-repair

> to fix a deep water cable, the ship has to use a grapnel, which grabs and cuts the cable, dragging the two loose ends to the surface. If needed, one end can then be hooked to a buoy and the other end brought on board. Cable has to be added to make the repair, since there is not enough slack to bring the cable up and cut a piece out. After the cable is retrieved and on board, in a repair room that looks like a laboratory, engineers repair the cable. Data cables can take up to 16 hours to repair, after which they are lowered back down to the sea bed in an omega or hairpin pattern to accommodate the extra length. There is new technology in development that would make in situ repair possible for power cables, preventing the need to pull the cables up to the surface.

(Second YT search hit so there might be better ones ) https://www.youtube.com/watch?v=FtEw19JX-UE

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