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Top: Submarine fibre optic cable
Left: Advances in cable technology mean that the interval between repeaters can be longer, making long-haul subsea cables cheaper Bottom: Fibre optic cable ready to be loaded on to the ship
oſten routed so that they are on the least risky route from things like fishing and anchoring and some geological hazards such as landslides and earthquakes and tsunamis. But the latency requirements mean that we need to look again at the route, in terms of the shortest route for the cables, and that sometimes means the customer will determine a compromise between the latency requirements and the actual avoidance of all the risks.’ If a company opts for the route, not with the
least risk, but the lowest latency, it has to make sure that it manages the risks and can cope with them. To address that challenge, mapping soſtware such as Geographic Information Systems (GIS) provides information on the infrastructure of the seabed. What is new now, says Wilson, is the drastically improved volume and quality of this information. More and more governments and research bodies publish data on fishing areas and seafloor sediments, and share it online with industry. ‘Tey have provided far more information in far more detail on what is happening on the seabed than they historically have done,’ says Wilson. ‘We can plan far better for cable routes by integrating all this information; it is now like Google Earth but for technical and engineering purposes.’ Once the route is chosen, companies then
decide on the appropriate selection of armoured cable and burial depths to prevent cable damage – something that is ‘also key to a stable cable system’, says Satoru Ito, a spokesman for KDDI, Japan’s second-largest telecoms operator. And there are other techniques too – Verizon, for instance, uses a GPS-based collision-avoidance technology called Automatic Identification System (AIS). It allows the firm to track vessels operating in the vicinity of submarine cables and, if necessary, make contact with a ship that ‘may be about to drop anchor on the cable, and
Issue 1 • Autumn 2013 FIBRE SYSTEMS 25
suggest a better anchorage,’ says Verizon’s Palmer-Felgate. ‘Tis pre-emptive communication has helped to improve the reliability of submarine cables in areas of high vessel activity.’ But problems may surface even on the most
carefully planned routes. Besides natural disasters, conditions at the time a cable was originally laid may not be the same a decade or so later. For instance, remembers Wilson, one of the cables off the UK coast that was laid when fishing trawlers used to reach the depth of 1,000m with their trawling gear was no longer safe several years later, because fishermen started using new technology that allowed them to go deeper – and possibly damage a cable down at 1,500m. ‘We had to go
Conditions at the time a cable was originally laid may not be the same a decade or so later
Global Marine Systems
TE SubCom Global Marine Systems
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