07 July 2017
| Alan Burkitt-Gray
MainOne’s cable from Portugal to west Africa is now in full operation again after what’s believed to be a landslide on the sea bed caused it to fail.
In a full, detailed report (PDF) MainOne says that
all services were restored in the early hours of 3 July thanks
to repair work by the French cable ship Pierre de Fermat.
MainOne says: "The cable has been tested to be in good
operating condition and we have restored all services to normal
operating conditions and provisioned additional capacity
wavelengths to address increased demand for internet connectivity
from our wholesale and enterprise customers across west
The cable, which was laid seven years ago as the first
broadband cable to serve west Africa, was cut at 05:18 on 18
"Initial investigation conducted into the failure of
communications on the fibre pairs into Portugal indicated a
fault on the submarine cable system, which was further
localised to a location about 3000km south of Portugal, where
the cable is at 3400m water depth," says the report. "This
assessment suggested that the outage was not a likely outcome
of external human factors such as a dropped ship anchor or
trawler fishing or sabotage since such activities generally do
not take place at such ocean depths."
The morning after the failure, the Pierre de Fermat was already
on the way from its home port of Brest, heading for Portland in
the UK to pick up spares.
The Pierre de Fermat arrived on
site a week later, and grappled up the broken ends of the cable
– showing a landslide was the most likely cause. The
slide "trapped and crushed the cable thus resulting in a cut to
both the fibre and power cables within the cable enclosure".
The damaged section was replaced with new cable from Portland,
which was spliced into the broken ends.
X-ray images of the final spliced cable showed good quality
joints. MainOne executive Bernard Logan – who has 30
years’ experience in the subsea cable industry,
since joining what was then STC Submarine Systems in 1986
– approved the powering up of the cable from the
terminal stations. "The vessel started the process of lowering
the submarine cable back to the seabed and [it was] guided into
After further tests once the cable was back on the sea bed,
"all the active wavelengths carrying traffic on the system were
again activated and verified and traffic started being restored
onto the cable system", says the report. "MainOne engineers who
had been on the sidelines in recent weeks were delighted to
have the system back in working order and within a few hours,
all services were restored back onto the cable system."
Pierre de Fermat