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So do we sometimes lay cables on top of other cables down there? What governments do you have to go to to get approval to do this? Could I just run a string ac

So do we sometimes lay cables on top of other cables down there? What governments do you have to go to to get approval to do this? Could I just run a string across the Atlantic Ocean? If we do lay cables on top of other cables how high do they get stacked? Are there challenges to bring the lower cables back up? Does that happen? Or do we just keep them down there forever basically and upgrade the hardware at the terminal?

wmf 2y ago
They don't bring the cables up unless a repair is needed. It's probably much safer to leave decommissioned cables on the ocean floor so they don't disturb each other.
staplung 2y ago
> So do we sometimes lay cables on top of other cables down there? I don't know exactly how often this has occurred but I'd guess it's relatively rare. The companies that operate in this space are very specialized and sophisticated. The locations of pretty much every cable laid in the last half century is very precisely tracked and one of the first things that has to happen when preparing a new cable route is to undertake a high resolution side-scan sonar survey of all or part of the planned route. In shallower water the cables are typically buried under several meters of the seabed. > What governments do you have to go to to get approval to do this? Could I just run a string across the Atlantic Ocean? At the very least you'll need to have landing agreements with the countries at the various endpoints. In international waters I believe there are some laws that apply but I gather that it's more about liability. You'd have a lot of difficulty running a string across the Atlantic. Controlling the amount of slack on a cable that's being played out is incredibly finicky work. Keep in mind that the point where your hypothetical string is touching down on the sea bed might be several miles behind where you are and that your ship is going to be bobbing around on the surface and you get an idea. > If we do lay cables on top of other cables how high do they get stacked? Are there challenges to bring the lower cables back up? Does that happen? Or do we just keep them down there forever basically and upgrade the hardware at the terminal? Cables are routinely brought up for repair or disposal. The ships that do this are called Agreement ships. In 1866 the second-ever transatlantic cable was grappled up to the surface and repaired (it snapped while laying it the previous year). Modern cables are fiberoptic and do not increase their bandwidth once laid.
- toast0 2y ago
  > The locations of pretty much every cable laid in the last half century is very precisely tracked and one of the first things that has to happen when preparing a new cable route is to undertake a high resolution side-scan sonar survey of all or part of the planned route. When the cables aren't well buried, they can migrate. No link, but earlier today I saw a description of a repair that was significantly delayed because the cable ends were 15 km away from where they were expected to be. That said, I think there's a lot of area on the sea, and not a lot of cables, so chances of overlapping are low; especially if a survey is done of the new route immediately before. Although if they're buried, maybe you can't see them so well. And a little overlap here and there probably isn't a big deal, because most of the time cables are brought up, it's because they were severed, so likely it doesn't disturb the other cable too much on its way up.
  - lxgr 2y ago
    Overlapping is guaranteed in at least every case where a new cable has a more southern/western terminal on one but a more northern/eastern terminal on the other continent as an existing one. No idea if specific care is taken to avoid that, or if it's even a problem, but I could imagine so for cables that are buried in the seabed – the act of burying the new one could damage the existing one. But cables are only buried in shallow waters, is my understanding (where there's high risk of an anchor destroying them), so as long as the point of overlap or intersection is in deep seas, I'd imagine it to not be a problem.
    - dguest 2y ago
      Yeah it's a 2d geometry, of course some of the cables will cross. The other reason that overlapping would be an issue is if they need to pull up a section to repair it and it's directly under another cable. But the ocean is really damn big and there are only O(100s) of submarine cables. In both the burying in shallow water case, and the deep water maintenance case, I'm guessing the chances of two cables being in the same place is very very small.
  - RoderickBeck 2y ago
clown_strike 2y ago
> What governments do you have to go to to get approval to do this? It's a good question, the ocean being international waters and all. I dont know that answer but for [geosynchronous] satellites in orbit this is negotiated with affected countries via the ITU. (Create a mesh of undersea cables dense enough and you end up with a tripwire for submarines...)
Angostura 2y ago
It's possible that the ITU might still be involved. https://www.itu.int/ https://www.itu.int/
cruffle_duffle 2y ago
If one is north south and another is east west, then they have to cross each other.
RoderickBeck 2y ago
In international waters you do not permits. Only for landing the cable and in the territorial waters. - The Author.

wmf 2y ago

They don't bring the cables up unless a repair is needed. It's probably much safer to leave decommissioned cables on the ocean floor so they don't disturb each other.

staplung 2y ago

> So do we sometimes lay cables on top of other cables down there? I don't know exactly how often this has occurred but I'd guess it's relatively rare. The companies that operate in this space are very specialized and sophisticated. The locations of pretty much every cable laid in the last half century is very precisely tracked and one of the first things that has to happen when preparing a new cable route is to undertake a high resolution side-scan sonar survey of all or part of the planned route. In shallower water the cables are typically buried under several meters of the seabed. > What governments do you have to go to to get approval to do this? Could I just run a string across the Atlantic Ocean? At the very least you'll need to have landing agreements with the countries at the various endpoints. In international waters I believe there are some laws that apply but I gather that it's more about liability. You'd have a lot of difficulty running a string across the Atlantic. Controlling the amount of slack on a cable that's being played out is incredibly finicky work. Keep in mind that the point where your hypothetical string is touching down on the sea bed might be several miles behind where you are and that your ship is going to be bobbing around on the surface and you get an idea. > If we do lay cables on top of other cables how high do they get stacked? Are there challenges to bring the lower cables back up? Does that happen? Or do we just keep them down there forever basically and upgrade the hardware at the terminal? Cables are routinely brought up for repair or disposal. The ships that do this are called Agreement ships. In 1866 the second-ever transatlantic cable was grappled up to the surface and repaired (it snapped while laying it the previous year). Modern cables are fiberoptic and do not increase their bandwidth once laid.

toast0 2y ago
> The locations of pretty much every cable laid in the last half century is very precisely tracked and one of the first things that has to happen when preparing a new cable route is to undertake a high resolution side-scan sonar survey of all or part of the planned route. When the cables aren't well buried, they can migrate. No link, but earlier today I saw a description of a repair that was significantly delayed because the cable ends were 15 km away from where they were expected to be. That said, I think there's a lot of area on the sea, and not a lot of cables, so chances of overlapping are low; especially if a survey is done of the new route immediately before. Although if they're buried, maybe you can't see them so well. And a little overlap here and there probably isn't a big deal, because most of the time cables are brought up, it's because they were severed, so likely it doesn't disturb the other cable too much on its way up.
- lxgr 2y ago
  Overlapping is guaranteed in at least every case where a new cable has a more southern/western terminal on one but a more northern/eastern terminal on the other continent as an existing one. No idea if specific care is taken to avoid that, or if it's even a problem, but I could imagine so for cables that are buried in the seabed – the act of burying the new one could damage the existing one. But cables are only buried in shallow waters, is my understanding (where there's high risk of an anchor destroying them), so as long as the point of overlap or intersection is in deep seas, I'd imagine it to not be a problem.
  - dguest 2y ago
    Yeah it's a 2d geometry, of course some of the cables will cross. The other reason that overlapping would be an issue is if they need to pull up a section to repair it and it's directly under another cable. But the ocean is really damn big and there are only O(100s) of submarine cables. In both the burying in shallow water case, and the deep water maintenance case, I'm guessing the chances of two cables being in the same place is very very small.
- RoderickBeck 2y ago

clown_strike 2y ago

> What governments do you have to go to to get approval to do this? It's a good question, the ocean being international waters and all. I dont know that answer but for [geosynchronous] satellites in orbit this is negotiated with affected countries via the ITU. (Create a mesh of undersea cables dense enough and you end up with a tripwire for submarines...)

Angostura 2y ago

It's possible that the ITU might still be involved. https://www.itu.int/ https://www.itu.int/

cruffle_duffle 2y ago

If one is north south and another is east west, then they have to cross each other.

RoderickBeck 2y ago

In international waters you do not permits. Only for landing the cable and in the territorial waters. - The Author.