Back Reflection Images courtesy of Atlantic-Cable.com
Submarine Cable Ploughing Since the advent of fibre optic technology, the burial of submarine systems on continental shelves to protect against external aggression has become ubiquitous. However, in an industry that celebrates its 160th birthday in August this year, simultaneous lay and plough (plow) burial is a relatively young technology. For the majority of the telegraph and telephony eras, cables were surface laid and external aggression was managed by heavy armour cable protection and network diversity.
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Although a number of attempts to bury submarine telegraph cables on the UK continental shelf were made in the early part of the 20th Century, it is general accepted that it was the Western Union Telegraph Company that was the first company to develop a viable ship-towed cable plow. By the end of the 1930’s, Western Union had completed development of its design and concluded that a trench depth
by Stewart Ash & Kaori Shikinaka
of no more than 10 inches (25cm) would be practicable, given the tow forces that would be necessary. In 1938, this plow was deployed from the Cable Ship Lord Kelvin off the coast of Ireland to bury sections of three of Western Union’s transatlantic telegraph cables. Another 20 years was to pass before, due to the number of faults caused by fishing, to TAT-1 (1956) and TAT-2 (1959) on the eastern continental self of the USA, it became apparent to the system owners that some improved form of protection was necessary. From the early 1960’s, Bell Labs, on behalf of AT&T, developed a series of plough systems (Sea Plow I to V) which were used in the 60’s and 70’s to bury AT&T’s transoceanic telephone cables. These plough designs, owed much to the Western Union plow, they produce an open trench of 24 inches (60cm), and could operate to water depths of 500m. In the Far East, the first ploughing of a long haul submarine cable took place on
the 1976 East China Sea Cable (ECSC). The equipment used was a multi blade plough, developed by the KDDI group and towed by the KDD Maru. It was capable of a burial depth 60 – 70 cm, in water depths down to 200 metres. This PLOW was also used during the laying operations for the Okinawa - Taiwan cable in 1979, Japan Korea and Kuantan – Kuchin in 1980 and the MST cables in 1982. By the early 1980’s, fibre optic technology was promising system owners an unheard of increase in cable system capacity. At the same time, commercial fishing was becoming more intensive; trawlers were getting larger and were operating in greater water depths. This combination made system security an increasingly significant consideration. In the UK, British Telecom International (now BT) conducted a thorough investigation into the risks to submarine cables for external aggression in the English Channel, North Sea and on the Atlantic Continental Shelf.