Undersea Cable Repair Via 19th Century Tech

An anonymous reader writes to mention a story going across the wires about an old-fashioned way to fix a modern convenience. Taiwanese boaters are using simple hooks to fish up the fiber-optic cables damaged in an earthquake late last year. The outage that resulted kept millions of users offline in half a dozen countries around the Pacific rim. From the article: "They work 24 hours a day but the weather can hinder their progress. Walters said one ship is waiting for 30 to 40 mile-an-hour winds (48 to 64 kilometres- an-hour) to die down in the Bashi Channel. The winds have stirred up 10 to 12 metre waves ... After arriving at the scene they survey the ocean bottom to assess whether the contour has changed, and the degree of sediment movement. Then the traditional tools are brought out. A rope with a grapnel on the end is played out, down into the depths, and towed over the sea floor until tension registers on a graph on the ship, indicating contact has been made with the cable. Today's fibre optic cables are just 21 millimetres in diameter."

Comments

Get with the program

[dangitman]

What, are they Amish or something? Every modern company uses sharks with friggin' lasers to repair optical cables.

No Electronics?

[SageMusings]

I beg to differ. There are devices known as OTDRs (optical time-domain reflectometers). Essentially, you shoot a pulse of light down the carrier and start a high-speed counter. The difference in refraction (say, a break in the cable or the end of the cable) causes a reflection that is detected at the device. Using the elapsed time, you get the distance to the break.

Check out this link http://en.wikipedia.org/wiki/Optical_time_domain_r eflectometer

I also saw a documentary on the Science channel about these ships. The whole process of fixing the break is sterile and professional. They use fusion splicers, which fuse the two ends with an electric arc. Fascinating stuff.

Re:No Electronics?

[rjforster]

Disclaimer: I used to build the pump lasers for the submarine repeaters so I know something about this. I also have a fibre optics PhD and have made more fusion splices than I care to count.

OTDR only works if there are no isolators in the path. (Gizmos which let light pass in one direction only)

In some submarine cable designs at each repeater there is a return path (ie a fibre loops back) going back the way the light came. I seem to remember this being at an out of channel wavelength (so it passes through some wavelength dependent isolators). Anyway, once you know how many repeaters you do get light back from along this return path you know more about where the break is.

I was surprised by the comment about the cable thickness for working at 2.5 miles depth. The repeater chassis I've seen are steel, coffin sized, and the walls are 21mm thick.

I also have a feeling that todays technology is the same as that of 4 or 5 years ago. There hasn't been that much investment (or new jobs) in new submarine cable tech since the dot-com crash. Maybe it's picking up again now but it will take a while to get the momentum back that we had in the R&D team 6 years ago.

Re:No Electronics?

[mike_in_nj]

Disclaimer: My father worked for several firms involved in the manufacture, laying, and operation of submarine cable systems in the 80s and 90s. I've seen and handled the cables and have toured the type of ship shown in the photo.

The cable size (21mm) sounds correct. They are much smaller than the repeaters. I've seen some samples mounted on display plaques so that you can see how they are constructed. Each cable contains a small number of tiny fibers (the ones I've seen had 6). The construction is a solid metal (steel?) core for strength, then some sort of thicker plastic layer around it that contains the fibers embedded within it, then a copper shield layer, and then more of the plastic material. I've probably missed a layer or two.

On the deep sea floor, that's all there is. Just one of those cables (not bundled or armored) with the big repeater casings every so often. At shallower depths, they can be armored to prevent damage from sharks. (Sharks like them, don't know why.)

The ships are pretty amazing. They have large bow and stern thrusters and can hold position in some pretty rough water. They have huge, round vertical cylindrical holds into which the cable and inline repeaters are fed in and spooled from the factory, and then fed back out when laying them at sea. There's a giant conveyor mechanism that runs from bow to stern to facilitate deployment or recovery of the cable and repeaters. This conveyor clamps onto the cable from above and below it, but it can also widen dramatically to accommodate the repeaters as they pass through.

Interesting that they use a line and a grapple to find and recover the cable, but they do have very precise survey maps to work from that were created when the cable was originally laid, so they probably don't have to look very far to locate it.

Actually...

[kamapuaa]

Actually, it didn't keep people offline in Asia. It just made international Internet connections incredibly slow. Using the Internet for national sites, which is the vast majority of Internet use, was barely effected. Here in China, nobody at my American-owned computer company even cared, except that MSN chat was pretty spotty for a couple days.

Re:21 mm?

[Bios_Hakr]

The don't just have fibers either. There is a central core; usually steel cable. Then they have power feeds for the repeaters. Every 50~100km, they'll have a repeater pod. Finally, they have the fibers and, on top, a thick metal or plastic sheath.

What's really amazing about undersea cables is that no one outside the industry really thinks about them. Sprint and ATT give everyone the impression that sats take care of most comms. However, the opposite is mostly true. The vast majority of comms are way too time sensitive to allow the the delay imposed by satcom.

Re:huh

[amorsen]

It's reasonably easy to find a cable. At those depths the cables lie directly on the sea floor, and if you run a hook across the sea floor from one side of the cable to the other, you'll cross it by definition. Sure you might then end up some distance from the break, but they are apparently reasonably good at handling that. Such techniques don't work with shipwrecks -- and even if they did, there may not be anything the right shape for a hook to catch.

Anyway, there's an old but interesting article on undersea cables by Neal Stephenson.

Re:21 mm?

[Anonymous Coward]

What's really amazing about undersea cables is that no one outside the industry really thinks about them.

That's the way any engineering works if it is well designed. Most people don't think too much about how a hydroelectric or coal power plant works either. Nor do most people today care about how an interrupt controller works.

It sort of sucks for the engineer because you are in the position where you are only recognized if you frack up (and yes I've been in BSG withdrawal). The best type of award you can get for your accomplishments (other than a big fat paycheck) is for nobody to ever think about what you did. Case in point: everyone remembers the dipshit who invented the square wheel, but nobody ever gives recognition to the genius who invented the round wheel.

And what exactly would be a modern way?

[Josef Meixner]

When a method works well, there is not really a need for something else, it will only be used when it is superior. So what would those alternatives be, that are cheaper overall?

A submarine robot repairing on site is probably not possible (I have problems believing it would be able to fuse the fibers), so you only could use it to more quickly find the cable and perhaps make it easier to get the hook onto it as you can see what you are doing. But honestly, how much faster would it be, I guess a hook and the cable for it can just be tossed into the water, an expensive robot probably would take a bit longer to reach the ground. And it probably has limitations on the depth it can operate. Additionally I am quite sure they don't just drive out there and plow the sea bed, they probably have a very good idea where the cable is supposed to be. And don't forget, to find a very long cable is much simpler than finding a wreck. I don't have to find a particular piece, any piece before and after the break is ok, as I can just pull the part up and then follow it, no need to exactly grab the end.

Also the strong winds and high waves probably would make fusing the cables very hard as well, even if they could bring up the cable. So the only thing 'old fashioned' I can see is, that they use a hook. The rest is probably quite up to date and the hook is simply the easiest, most reliable and cheapest way. Why use expensive technology if something simple is perfectly adequate?

Is this newsworthy?

[andrewdotcoza]

I don't want to seem overly flippant, but is there really something significant about mariners using hooks to pull stuff out of the sea? I'm not really clear what the alternatives were. I'm expecting "Man Digs Hole With Spade" and "Tech Professional Presses Distant Button With Pointed Stick" as future headlines. OK. I admit that was overly flippant.