History of the Atlantic Cable & Undersea Communications
from the first submarine cable of 1850 to the worldwide fiber optic network

by Stewart Ash


On 4th May 1986, the first international fibre optic submarine cable system went into service. UK – Belgium No. 5 was purchased by a consortium of British Telecom International (BTI), Deutsche Bundespost (Germany), PTT Telecommunicatie (Netherlands) and Regie TT (Belgium) from STC Submarine Systems Ltd (UK).

At the close of the coaxial analogue system era, STC (now part of Alcatel-Lucent) was the leading supplier of submarine cable systems world wide, commanding 50% of the available market. STC’s standard product at that time was its 14MHz system, which offered purchasers a capacity of 1,860 x 3KHz voice channels. UK – Belgium No. 5 was in another league all together, providing a design capacity of 11,520 x 64 kbit/s voice channels.

UK – Belgium No. 5

The system connected Broadstairs in the UK to Ostend in Belgium, a route length of 113km. The cable contained six nylon-silgard-covered mono mode fibres operating in pairs to provide three separate transmission systems. Transmission per fibre pair was at a wavelength of 1,310nm and the data rate was 280Mbits/s. To make the crossing the signal had to be regenerated three times by means of three repeaters powered from the terminal stations with a line current of 1.5Amps.

CS Alert

The shore ends at Broadstairs and Ostend were installed by the Dutch vessel DG Bast in September 1985. The main lay operations were carried out by the BTI cable ship Alert, free-issued to the system supplier. The cable was loaded at STC’s Southampton factory, where the three repeaters were spliced into the cable on board ship, and System Assembly and Test (SAT) was completed before the ship sailed.  Jointing repeaters and conducting SAT onboard the vessel was standard practice during the analogue era.

UK – Belgium No. 5 Repeater Being Housed

The North Sea at that time was very heavily fished by big trawlers, and because of the then massive traffic carrying capacity of the cable, it was decided to further protect the cable by burial. Although this is common practice now, prior to UK – Belgium No. 5, coaxial cables deployed in the North Sea were heavily armoured and the cables were surface laid. Operators relied on route diversity to tolerate the inevitable cable breaks. Plough burial in European waters was yet another first for UK – Belgium No.5.

The cable was installed in the spring of 1986 and buried using a plough designed and developed by BTI that achieved an average 0.75m burial depth over 86km of the route. The plough system was very similar to those used to today; however, there was one major difference. The cable and repeaters were delivered to the plough via a system of guide tubes suspended from the plough’s tow rope. And the rest, as they say, is history!

Article text copyright © 2016 Stewart Ashsh

Return to the index of Stewart Ash’s Back Reflection articles

Last revised: 22 September, 2016

Return to Atlantic Cable main page

Search all pages on the Atlantic Cable site:

Research Material Needed

The Atlantic Cable website is non-commercial, and its mission is to make available on line as much information as possible.

You can help - if you have cable material, old or new, please contact me. Cable samples, instruments, documents, brochures, souvenir books, photographs, family stories, all are valuable to researchers and historians.

If you have any cable-related items that you could photograph, copy, scan, loan, or sell, please email me: [email protected]

—Bill Burns, publisher and webmaster: Atlantic-Cable.com