Subsea cables: what happens when they’re damaged?

We live in an interconnected society, driven by the growth of our dependence on gadgets. However, despite this dependence, glitches still occur and technology can fail us from time-to-time. While the most we have to deal with is a smashed smartphone screen or an unresponsive laptop, what happens if the problem is located deep on the ocean floor?

The world has over 350 subsea cables, totalling 550,000 miles. They help to connect countries to the internet and, as such, we’ve become dependent on them — but what happens when these essential connections are damaged? 

You may think they’re protected being buried deep under the ocean floor, but the cables are actually vulnerable to all sorts of damage — and the impact it can have is huge. 

Join subsea cable laying company, Fraser Hydraulics, to find out how these vital cables become damaged, the impact this damage has and the implications of repairing them:

The potential damage

Damage can be caused to subsea cables in several ways. It is estimated that 70% of cable damage is caused by ship anchors. Despite having access to maps showing where the subsea cables lie, incidents can still occur where anchors are dropped and cables are ruptured. 

Nine countries across East Africa, the Middle East and Europe were left without connections as cables linking the countries were severed twice in the space of a month. More recently, 2016 saw four of the eight cables between Folkestone and Calais severed as a result of Storm Angus, reducing electricity flow by half.

Cables can also be damaged by fishermen and earthquakes, tsunamis and other natural disasters. Other causes are more unusual. In 2013, a fire broke out in Alexandria, Egypt, damaging six of the coastal subsea cables. It had a huge impact, causing internet outage across many East African countries, highlighting how multiple cables in the same area can be risky should damage occur. 

Sharks have been known to damage the cables too, with Google reinforcing their internet cables in 2014. Experts believe the signals sent via the fibre optic cables create motion, much like the movement of fish, attracting the predators to them.

Although it has never happened before, damage to subsea cables as a result of an act of terrorism can never be fully ruled out either. 

How are subsea cables repaired?

It’s important that damaged subsea cables are repaired quickly, in order to minimise the impact of lost connectivity. The cost of this repair work is dependent on a number of factors, which will vary depending on the severity of damage and the positioning of the cables involved. 

When cables are damaged, cableships are in place at key locations to increase the speed of response. With continuous monitoring, it’s easy to detect changes within a cable system, which could indicate damage.

Given their location, fault detection depends on the cable stations at each side of the cable system working collaboratively. Once located, details are passed to the cableship, which is loaded with the necessary equipment and sent to carry out the repair. 

A hook-like device called a grapnel is towed along the seabed, with the aim of hooking the cables. The cable can then be raised and repaired. For deeper sections, an ROV may be used.