Submarine Communications Cable

What is a Submarine Communications Cable?

The fiber optics and strands of glass are common and consistent elements of all the submarine communications cable, which is not much thicker than hair. Data can be transmitted along these strands via wavelengths of light, at the speed of light and over hundreds of kilometers without interference.

Each of these fiber optic strands is able to carry large amounts of information. The latest technology could potentially provide upwards of sixty 400Gb per second channels down just 1 no. fiber optic strand. To try and quantify that, that is enough capacity to carry 375 million simultaneous telephone conversations on 1 no. fiber optic strand. The number of fiber optic strands in a cable varies, usually dependant on length, from around 4 - 8 for a Trans-Atlantic cable, but up to 200 for a cable across to Europe.

Generally subsea cable is no larger than 60mm dia. The remainder being made up of a polyethylene insulating/water proofing material, a copper core (needed to transmit power to signal boosting equipment), and potentially varying combination types of steel armour wires - depending on location and application of the cable on the sea floor.

How are submarine cables Installed?

Where possible, and necessary, the preferred option is to bury the submarine cable under the sea floor. This is usually on the continental shelf where it is shallow enough for the cable to be damaged by ship's anchors or commercial fishing.

There are various methods of doing this, but the one most often used is a cable plough

The plough is towed by a cable ship, like the one above, it lifts a furrow of the seabed and the cable, fed from the ship's hold, slides into this furrow, after the plough passes the part of the seabed that was lifted, it is returned back to the seabed on top of the cable. Burial depths vary according to seabed conditions. In some cases it may not be possible to bury a cable, for example where there is hard rock. In these situations other methods of protection may be considered, such as, increased armour to the cable construction, protective outer casings, covering with graded material or covering with modular protective units of polyurethane or concrete.

In some cases it may be that there is no need to protect the cable and it may be laid directly on the sea floor, which is largely the case in deep oceans.