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The impressive submarine cables (second part)
In first place, prior to the installation of the cable, the path must be planned to avoid threats, like fishing areas, previous installations, the rocky outcrops of the oceanic ridges, etc.
To avoid that the breaks and the waste due to factors like the rub on the rocks and the sand currents, there are two techniques: bury the cable (normally to 3 meters below the seabed and only when the deep and the conditions allow it), and/or cover it with an armature when is built.
There are distinct type of covering depending of the deep and the conditions of the zone where will be installed. These have less weight when goes deeper. For instance, in rugged zones as the oceanic ridges, is used a special kind of armature with abrasion resistant covering and with light weight. Also, in these zones, there are 10% more of cable needed due to the undulations and deflections of the terrain.
In the following photo you can see some types of cables. Although can't be appreciated, there are about 12 optical fiber cables inside of every one:
Regarding to the repeaters, every 60 or 350 Km approximately (depending of the quality of the optical fiber) there are to put one that regenerates the signal because the light goes lossing intensity, due to impurities of the fiber and to the bouncing of the light inside of the cable. Together to the optical fiber cables there are high voltages cables with the electrical current of the repeaters (the cables with colors of the following image).
These supply a constant electrical current because the repeaters don't have batteries.
Next you can see a photo of several repeaters that can stand high pressures.
To make a bifurcation that leave the signals on the earth the following brancher units are used:
To finalize here I left a documental of the Discovery Channel where is showed the process of installation of the cable from the boat "Ile de Batz" of the enterprise Alcatel-Lucent, that have 3 boats of this type. To install 200 Km. of cable, of the 4.000 that can carry the boat, must spend between 30 and 40 days in the sea.
You think in the work that must suppose perform the installation of the submarine cable more long until the moment (39.000 Km), the seamewe-3, which passes from Germany (Nordem) to South Korea (Keoje) and connects 32 countries, touching earth in 39 points.