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Comment by josh2600 | Hacker News Reader

http://mikesenese.com/DOIT/wp-content/uploads/2011/11/Unders...

^undersea cables are typically made up of a central fiber line, which look like human hairs in a small tube, and a shell of insulation and copper. You need power to send the signal across the ocean floor and, as we do not generate electricity underwater, all of the current needs to be sent from one end to the other to power all of the repeaters along the way.

The fiber optic cable is 17mm, but the cable itself can't be because of the power constraint (unless I'm missing something deep; feel free to correct me if so).

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> The nearer to the surface you get, the more protection—armour—you need to withstand potential disturbances from shipping. Trenches are dug and cables buried in shallow waters coming up onto shore. At greater depths, though, areas such as the West European Basin, which is almost three miles from the surface, there’s no need for armour, as merchant shipping poses no threat at all to cables on the seabed

http://arstechnica.com/information-technology/2016/05/how-th...

Fishing trawlers are more likely to cause damage: By far the most common problems, however—accounting for about 60 percent of cut cable incidents—are dropped anchors and fishing nets.

The cables are on sea charts so this can be avoided, but that won't stop deliberate saboteurs. The strategy for safeguarding undersea cables has been described as “security through obscurity.”

http://www.wired.com/2015/10/undersea-cable-maps/

Not very obscure if you can find them on a sea chart.

In normal power distribution, much of the cost is in generating the electricity, and the cable is cheap and readily accessible and you can easily take several truckloads of heavy cable to the many sites.

Undersea cable is different, and I suspect that nobody cares if 99.9% of the power is wasted to heat the power wire as long as enough gets to the repeaters.

Kirchhoff's law says that if your wire is insulated, ask the current that goes in one end comes out the other. The only thing is that you need to provide sufficient voltage to push it through the long wire.

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