5 days ago
How are undersea cables repaired? A look inside the WACS operation
Major internet issues have South Africans across the country following reports of undersea cable failures.
Image: Unsplash
Don't send angry emails to your ISPs just yet, because if your internet connection has been feeling a little slow, it might be because the West Africa Cable System (WACS) has been offline since June 1.
WACS is a key internet artery linking South Africa to Europe and is reportedly offline due to emergency maintenance expected to last over two weeks.
The issue is a faulty branching unit near Swakopmund, Namibia, which supplies power to sections of the cable, resulting in slower speeds and connectivity issues, particularly in parts of the Western Cape, as providers reroute traffic through alternative routes like Seacom and EASSy on the East Coast.
Emergency maintenance began at 2am on June 1 and is scheduled to end by 8am on June 16, weather permitting.
During this time, the affected stretch of WACS is offline, meaning no data traffic can flow through it.
After replacement, engineers must run post-repair signal tests from South Africa to Lisbon and onward to London before declaring the system operational.
It's worth noting that the cable didn't break, but it's still useful to know how these fixes are done
How are undersea cables repaired?
Do you know how, when you have a problem with your laptop, you call IT and they tell you to switch your device off and on again? While this may work for computers and laptops, the same thing cannot be said for undersea cables.
Submarine cable repairs are high-stakes, logistically intense operations, as these cables can stretch thousands of kilometres across oceans, which makes repair work highly specialised, time-consuming, and dependent on good weather.
This is how it goes down, according to One Step Power.
1. When a cable goes down, engineers first use signal tests to identify the break. A pulse of light is sent through the fibre. Under normal circumstances, the light travels uninterrupted, but when there's a break, the light reflects. From this, engineers can pinpoint the problem area. For power cables, they sometimes use remotely operated vehicles (ROVs) with fault detection tools.
2. Once the damage is located, a specialised cable repair ship is sent to the area. These ships are fitted with dynamic positioning systems that keep them steady in rough seas. They're also stocked with replacement cable that is usually around 5–10 km. Newer vessels can carry up to 9,000 km.
3. In shallow water, ROVs with cameras and robotic arms can grab the cable and bring it up. However, in deep water where pressure is too high for ROVs, a deep-sea fishing hook called a grapnel is used to cut and haul the cable ends to the surface. These ends are either brought onboard or floated with buoys until the ship can complete the fix.
Once on board, the cable is moved into a repair room, where engineers clean, splice, and test it. The process can take up to 16 hours. The repaired section is then lowered back down, often in a hairpin or omega loop to accommodate the extra cable length needed for the operation.
In this case, Openserve confirmed that a repair ship successfully located and recovered the faulty branching unit. Engineers onboard confirmed that the cable itself is intact.
How WACS works and why it matters
WACS is a 14,530-km-long submarine fibre optic cable that runs from Portugal to South Africa. It has landing points in 11 countries, including Namibia, Angola, and Ghana. It has a design capacity of 14.5 Tbps and includes dedicated express lanes, which are direct high-speed links between South Africa and Europe, making it a vital resource for ISPs and content delivery networks (CDNs).
When WACS is compromised: Traffic must be rerouted, often through longer or more congested paths.
Latency increases, especially for international content.
Regional imbalances emerge — Cape Town ISPs are more affected than Gauteng-based ones, due to routing differences.
Once the faulty branching unit is replaced, it will be sent to the supplier for analysis to determine what went wrong. While the cause remains unclear, operators hope no further complications arise during testing.
If all goes well, normal traffic should resume by Sunday.
IOL
