TAT-8

From Wikipedia, the free encyclopedia
Jump to: navigation, search

TAT-8 was the 8th transatlantic communications cable, initially carrying 40,000 telephone circuits (simultaneous calls) between USA, England and France. It was constructed in 1988 by a consortium of companies led by AT&T Corporation, France Télécom, and British Telecom. It was able to serve the three countries with a single trans-Atlantic crossing with the use of an innovative branching unit located underwater on the continental shelf off the coast of Great Britain. The cable lands in Tuckerton, New Jersey, USA, Widemouth Bay, England, and Penmarch, France.

The system was built at a cost of US$335M in 1988 and retired from service in 2002.

This was the first transatlantic cable to use optical fibers, a revolution in telecommunications. The system contained two working pairs of optical fibers. (A third was reserved as a spare.) The signal on each optical fiber was modulated at 295.6 Mbit/s (carrying 20 Mbit/s traffic) and fully regenerated in equipment placed in pressure housings separated by about 40 km of cable.

There were several problems with the early reliability of this cable during its first 2 years of operation. The cable was buried on the continental shelf on the European and the American side of the ocean. it was snagged and damaged by fish trawling fleets where burial was ineffective. AT&T laid a trial optical cable in the Canary Islands in 1983. This cable did not have an electrical screen and was attacked by sharks. It was never proved whether these attacks was due to the sharks sensing the electrical radiation from the cable or the vibration of the cable moving on the sea floor where it might have been suspended. TAT-8 did have the screen conductor because of the possible effect of the shark attack. Because the cable was the first fiber optic cable and not coaxial cable, the electrical interference shielding for the high voltage supply lines was removed. This removal did not affect the fiber, but it did cause feeding frenzies in sharks that swam nearby. The sharks would then attack the cable until the voltage lines killed them. This caused numerous, prolonged outages. Eventually, a shark shielding was developed for the cable. PTAT-1, the next cable to go in the Atlantic was put in with the shark shielding and it proved much more reliable than TAT-8.

The system was manufactured by a consortium of three established submarine system suppliers: AT&T, STC and Alcatel. The idea was that each manufacturer would manufacture part of the system, so French technology procured by France Télécom would land in France, US technology in America procured by AT&T and British technology procured by BT in the UK. The systems were designed to interoperate although the regenerator supervisory systems were all proprietary. Transition between one supplier to another supplier's regenerators was achieved using a "mid-span meet." AT&T was appointed the Integration co ordinator and integration trials were held in Freehold New Jersey.

References[edit]