How do American phone companies connect to Asian phone companies? I assume that a couple satellites don’t have enough “bandwidth” to transfer all this information so… how do they do it?
Thanks
polloloco
Big fiber optic cables stretched along the bottom of the ocean.
Submarine telphone cables form a vast network all over the planet. There are two main reasons for having this cable network. One is that to just rely on a satellite network means that if somebody shot all these out of the sky with missiles you would be without any international comms. The other is the time delay of satallite links. To link some parts of the world together would mean having to go through two satellites which causes such a time delay that two-way conversations are almost impossible.
Big cables.
As an example, I believe that there are two cables that run from Australia direct to the US (one goes through Hawaii and the other direct to the mainland), and one cable that runs to the US via Singapore.
I seem to recall that they’ve almost completed another link, but I could be wrong. These cables carry both voice and data - several months ago, there were serious delays in international internet traffic in Australia because one of the cables broke (fortunately, just offshore, so they were quick to fix it) and it was before the second US link was complete. But I could be wrong on this too.
Thanks guys! That really helped!
Anyone know of a site with more information on the cables? I don’t understand how they cross such barriers as the Mid-Atlantic trench. Are there parts of it that are not undergoing expansion? Is the location of the cables secret? What happens if a cable does break somewhere in the deep ocean? I think of the cables as an engineering miracle, but mostly because I don’t quite know how they work. Thanks!
Try this site for a very good description of submarine cables :-
http://www.wikipedia.org/wiki/Submarine_communication_cables
Also Athur C Clarke wrote a very good book in 1958 called " Voice Across the Sea which gives a very description of the early days of both undersea telegraph and telephone cables. Try and get hold of a copy.
An interesting (to me at least) and long article about the history and the state of the art (as of 1996) of undersea cables written by Neal Stephenson…
go here
An excellent java app that shows different backbone providers across the world. Select “both backbones” in the far right upper pulldown. Check out UUnet; Telestra, through Australia; and above.net. This shows pretty much exactly who has bandwidth where.
I’ve been wondering, obviously the analog audio signal is digitized and probably compressed before it goes a significant distance. Does anyone know what format it’s converted into, and what compression format is used? The bitrate of the resulting signal would also be nice to know.
Rhythmdvl: If a cable breaks, a ship has to go out and find the broken ends (long cables use repeaters ever 5km or so, each of which is designed to send out a verification signal of its own, so finding which part of the cable broke is pretty easy), track down the loose ends with some combination of sonar and electronic sensors, snag them and pull them up to the surface, then splice them back together and seal the whole thing up again.
Actually, deep sea breaks aren’t that common. Damage is much more likely to occur in shallower areas, especially where there is more ship traffic (on one project I worked on a few years ago, one of our cables kept getting cut by weighted fishing nets. The company purchasing the cable had paid compensation to the fishermen not to drop their nets there, but we suspected some of them were doing it intentionally to blackmail the company into making more payments). In these areas, the cables are coated with thick metal/plastic armor. Even this isn’t enough, however, to protect the cable if a large ship drops its anchor on it, so sometimes (particularly near busy port areas) the cable is buried as deep as 10m under the sea floor.
As for the trenches, armored cables can withstand depths up to 8000m, so they usually run straight down to the bottom (they never ‘hang’ the cable over the trench, if that’s what you’re thinking). The important thing, however, is for the cable to run perpendicular to the slope. If it’s laid at an angle, it can roll and twist, which will break it quite easily.