transatlantic cable, anyone?

Factual Questions
1

I’ve been reading a few websites on this, and find it amazing that in 1866 a cable was laid between north america and europe (granted, after several failed attempts). Soon thereafter many more cables were laid. What an amazing technological achievement for their day!

Anyway, for those of you who might know something about this, i have a few questions:

How often would these cables be severed, if at all? Imagine, one gnawing critter could take out the link. And how could this possibly be repaired?

Are these transatlantic cables still used, or is everything done with satellite now? Obviously any phone communication before the mid-60s had to be done through undersea cables.

2

Yes they still lay these things, a lot go through to Hawaii as well. They don’t get broken as often as you’d think and when they do they generally break closer to the shore. what they do is pick up one end and follow it tiil they find the break and then fix it. I don’t know if it’s broken all the way through.

3

Laying the cables is a big business.

The internet drives a lot of it. Look around you. Companies are laying a lot of fiber optic cable [it can handle voice but is mostly for data transmission]. There is a lot being laid in the Pacific as those island nations get connected.

4

satelites introduce a very significant delay and are mostly not used for voice but for TV signals etc where the delay does not matter.

All along there have been cables all over the place. Now of course they are fiber optic.

The difference between voice and data is non existent. Voice is coded as data and transported the same way.

Anecdote: during the early stages of WWII the English managed to cut the only cable from Europe to America that did not go through Britain. That way they could monitor German traffic. The Germans did not know their code had been broken and the English were reading their messages. (of course it was telegraph, not voice, that was carried by these cables).

5

What happens when they get to a deep rift or valley on the floor? Does the cable go into it or does it kind of hang/droop over top like a bridge? Or can they avoid those rifts/valleys completely in the first place?

6

I know one other fascinating tidbit about undersea cables, which I learned from countless hours of watching Gilligan’s Island as a kid:

If a cable washes up on the shore of a desert isle, you can saw it open, tap into it, and make free long distance calls (assuming you have access to a Professor to help you with the wiring).

7

and was the entire cable pre-fabricated and on board the ship, or was it in pieces they would connect together? or would they build the cable on the ship? what happens when the ship is laying cable and there’s a hurricane?

8

Transatlantic cable is one of the most impressive pieces of 19th Century technology. The first cooking stove was installed in the White House about 15 years before the first transatlantic cable and the President had to travel to the Patent Office to figure out how to install it. The transatlantic cables just seem really far ahead of their time.

One of the other amazing things about them is how they were often cut, in WWII and possibly WWI, by German submarines. There was a cable-cutter assembled on the front of many U-boats, looking a little like a saw. It’s always been a mystery to me how you would find a submerged cable without modern high-frequency active sonar, but somehow they did. I don’t know if they ever had all the cables down at the same time though.

9

Boris

Those cable cutters might be for cutting cables on tethered mines and anti-submarine nets.

10

Here’s a University of Houston site that discusses the first transatlantic cables:

http://www.uh.edu/engines/epi1425.htm

It appears to be a good site in general. I may have to spend some quality time there.

11

Nice link, Doc.

12

The only problem with tapping into the washed-ashore undersea cable is a) you must have the appropriate conch shells, and b) it will wash away during the next monsoon before you can accomplish anything useful.

Jokes aside, thank you for this utterly fascinating information. I never knew nor thought 'bout the undersea cables.

13

That is a good link, Dr. Jackson, but it raises a big question for me:

Why? I mean, was it seventeen hours of dots and dashes (which seems like a lot for 98 words) or seventeen hours of electrons pushing and shoving (which seems like a lot for nearly the speed of light?

14

The cables’ contribution to geoscience (it really was significant).

From Turbidites:

15

I wondered about that, too. I just figured that it was designed by the same guy who designed our WAN at work.

16

Apparently he gets a lot of work.

17

Actually, it was because the first cable was made entirely of copper, and sending messages 5000 miles accross copper takes a LOT of voltage, and it was extremely difficult to get messages accross at all due to the sheer ammount of resistence of that length of copper. The first one eventually stopped working, but some clever engineering in the subsequent ones made them much better.

Resistence isn’t an issue with fiber, of course.

18

AFAIK, the English cut the German cable by sneaking near shore and fishing for it with grapnels. Not exactly hi-tech but definitely hi-risk.

19

There’s a very long but extremely interesting article from Wired a few years ago by Neal Stephenson about transoceanic cables here. Highly recommended if you have the time.

20

Ok, here’s a question I can talk about, having spent some time working on undersea fiber optic cable projects (hence my name).

-There are lots of undersea fiber optic cables out there, connecting Europe, Africa, the Americas, Asia and Australia, and there are more being laid every year. One being laid between Japan, China and Singapore right now is designed to carry 1.2 Tbps.

-The cables can, and do, get severed or worn. This happens most often near the shore, and is usually caused by fishing trawlers or ships’ anchors being dragged over the cable (which usually only happens close to shore). Sometimes the cables are even damaged by fish trying to eat them. Two ways of avoiding damage are by armoring the cable and/or burying it. Armoring is usually done by wrapping layers of steel wire around the cable (an unarmored cable is about 22mm in diameter (not counting waterproofing), while a heavily armored cable can be up to 70mm thick). Burial is usually done if there’s a significant risk of something big and heavy (ship’s anchor or hull) hitting the cable. For example, the area around Singapore has a lot of ship traffic, and is relatively shallow, so we had to bury one of our cables to a depth of 10m under the (soft, fortunately) sea bed.

-If a cable does get damaged away from shore, the only thing to do is to go out in cable-laying ship, find the break, get a hook around the cable, pull it up to the surface and fix it. This is extremely difficult, time-consuming and expensive, so most companies prefer to make sure the cables don’t get damaged in the first place.

-Fiber optic cables can only carry a signal for about 50km, so the undersea cables need to use repeaters to receive, amplify and re-transmit the signal for another 50km. They are about 2m long and weigh about 400kg. The fibers are clad in a layer of copper which carries the electric current to power the repeaters, so copper resistance is still a problem to be considered.

-The cable is loaded onto the laying ship as a single unit (including repeaters), wrapped around several giant spools. The ship follows the course that’s been mapped out and plays out the cable over the side. The ships can work in fairly bad weather, but in extreme conditions they may disconnect the cable (at a repeater, I would guess), drop the end that’s already been laid, and come back to reconnect later.

-If possible, the route designers try to go around extreme geographical features (trenches, mountains, etc.), but sometimes it can’t be helped (you can’t go east of Japan without crossing a trench). In these cases, the cables do go all the way down and all the way back up again. The cables will work down to a depth of about 8000m. In planning a route, the designers have to be careful to lay the cable in the same direction as the sea bed’s slope, so it doesn’t roll downhill and get twisted. This requires some very accurate maps of the ocean floor.

Hmm… I guess that’s all I have time to write about now (my boss will be asking why my work isn’t finished yet ;)). Corrections and criticisms are more than welcome.

–sublight.