What Are Sub-Sea Cables?


It is easy to take our ability of communication for granted. In fact very few of us know that this is result of the vast amounts of man-power, effort and money used to construct the world’s sub-sea cables which lay hundreds of feet below us on the ocean seabed. Connecting together all the continents with the exception of Antarctica, these cables allow us to call friends and relatives overseas as well as use the internet among other things.

The first submarine communication cables carried telegraph signals before they began carrying data communications. In August 1850 the first subsea cable was laid across the English Channel and was made of copper wire coated in natural gutta-percha. The first message to be sent by subsea cable was from the Queen to the US President in 1858.However, many of these early cables were damaged by the application of excess voltage before cables were laid permanently after 1866.

Since the 1980s, each cable has used optical fibre technology to pass faster broadband signals. These cables are typically 69 millimetres in diameter and tend to be a lighter weight in deeper waters. The wire is typically insulated by a number of protective layers including copper, polycarbonate, petroleum jelly and steel wires inside a polyethylene casing.

There are over 1000 cables both domestically and internationally distributed throughout the world and these will vary in size depending on the depth they are placed. Some are buried so that they don’t get caught up in trawler nets or damaged by anchors. Cables can also be damaged by large sea animals such as sharks as fish bites have often been found, however cables are quite vulnerable to harsh weather conditions and earthquakes.

The largest of the underwater cables is the FLAG (Fiberoptic Link Around the Globe) cable which stretches 28,000 kilometres and links the United Kingdom to Japan via the Middle East. There are also several cables linking Europe to the US and Canada, the US to Asia and cables that interlink the islands such as the Philippines and the Caribbean. Cables surrounding Asia have been hijacked by pirates on one occasion with the T-V-H cable linking Thailand to Hong Kong and Vietnam being cut and used for scrap. Several cables were also damaged by the Japanese Tohuku tsunami in April 2011.

Subsea cables are extremely reliable and account for a high percentage of communication link ups by comparison to those of a satellite and count for 99% of the world’s communication methods due to their speed. For example; the maximum transmission bit rate of the first sea cables was 45 megabits per second.

However there are issues with subsea cables. Although they pose minimal environmental threat, they have been intercepted during wartime as the USA tapped into several USSR cables during the Cold War.

Although some cables are rendered out of use whilst those which are working require regular monitoring and repairs they play a pivotal role in the way we communicate.