Fibre-optic cable system operator Seacom expects its faulty undersea cable to be repaired at the end of this week, as the repair schedule remained on track.

However, the company cautioned that a number of external factors including location, water depth, ocean currents and weather made the cable outage "very difficult" to repair.

On July 5, Seacom reported that its service was down because a submarine repeater failure was experienced, resulting in service downtime between Mumbai, in India and Mombasa, in Kenya.

The repeater is a large, complex unit, essentially a large box of optical electronics. Repeaters are required to regenerate the light signal at certain intervals along the cable to ensure the quality of the signal.

There are 159 repeaters deployed along the Seacom cable. "These are enormously robust pieces of equipment designed for the harshest conditions. A failure is very unusual. It could be due to external forces such as rocks, landslides, which have caused the failure of this particular repeater. We will only know what caused the fault when the repeater has been recovered," Seacom South Africa GM Martin Sanne told Engineering News Online.

Seacom has been working with its partners on the repair programme, as well as seeking restoration alternatives to maintain adequate connectivity during the repair process.

The designated ship has been deployed to the location of the fault where it will locate the cable on the seabed.

Once located, the cable will be picked up and brought on board the ship to undergo the necessary repair. This will include cutting the cable to remove the affected part, and reviewing the physical integrity of the cable before proceeding with the initial splicing of the spare cable segment which has been tested and prepared while in transit on board the ship.

When the final splicing is completed, the entire system will be tested before the cable is lowered back in the water.

Part of this process will entail the reconfiguration of the power supply to shut down and isolate the affected length of the cable.

Seacom said that this would only have a minimal effect on the intra-African services, which remained unaffected by this outage.