From the BBC:
“How will Tonga's broken
internet cable be mended?”
(It is estimated that there are
more than 430 cables around the world, spanning distances of 1.3 million km
(800,000 miles))
An undersea fibre-optic cable
which connects Tonga to the rest of the world was severed during the eruption
of a volcano. New Zealand's ministry of foreign affairs says it could take more
than a month to repair the 49,889km (31,000miles) of cable in the South
Pacific. The undersea eruption - followed by a tsunami - led to Tonga's 110,000
people being cut off. A 2G wireless connection has been established on the main
island, using a satellite dish from the University of the South Pacific. But
the service is patchy, and internet services run slowly.
How will the cable be fixed? The
cable, which is operated by Tonga Cable, is believed to have broken about 37km
(23 miles) offshore. According to Reuters, fault-finding conducted by the
company in the aftermath of the volcano seemed to confirm a cable break. The
process of mending it is actually quite simple, according to principal engineer
at Virgin Media, Peter Jamieson, who is also vice-chairman of the European
Subsea Cable Association. "They will send a pulse of light from the island
and a machine will measure how long it takes to travel and this will establish
where the break is," he explained. Then a cable-repair boat will be sent
to the location of the first break. It will use either an ROV
(remotely-operated underwater vehicle) or a tool known as a grapnel (basically
a hook on a chain) to retrieve the broken end. That will be re-joined to fresh
cable on board the boat and then the same process will happen at the other end
of the break. If all goes well, the whole process will take between five and
seven days.
Why might it take longer?
(The specialised repair boat will
take a while to get to the islands)
It will take time to get a cable
repair boat to the archipelago and the closest one is currently stationed in
Port Moresby, Papua New Guinea - about 4,700km (2,900 miles) away. The
specialised boat, The Reliance, serves more than 50,000km (31,000 miles) in the
South Pacific. Experts will have to determine that the area is safe for the
boat and the crew, and that no more volcanoes are likely to erupt.
Do these cables break often? It
is estimated that globally there are up to 200 repairs carried out every year,
but natural disasters causing them are rare. 90% of breakages come from
fishing-boat nets or anchors. Increasingly, tracking technology is being used
to inform operators about any boats in areas likely to pose a danger to cables,
so that they can be contacted directly to warn them. Data cables are made up of
fibre-optic strands of glass, but much of the thickness of the cable is just
protective casing for the glass strands. Cables that run over a continental
shelf have to be buried between one and two metres deep. However, many just lie
on the ocean floor because they are too deep under the sea for much to damage
them The exception to this is
natural disasters, such as happened in Tonga. In 2006, an earthquake off the
coast of Taiwan broke a cable, and led to a loss of internet and international
phone services in the region.
How vital are these cables?
(Map of the world's sub-marine
cable network)
In Western countries, if one
cable breaks it is not a problem, because there are many others. The UK, for
example, has about 50 cables feeding data into the country. In Tonga, there was
just one. "Ideally you would have at least two cables as a minimum,"
said Mr Jamieson. "But cables are expensive and there is no drive for
Facebook, Google or anyone to build one there." Around the world it is
estimated there are more than 430 cables, spanning distances of 1.3 million km
(800,000 miles). After an earlier cable break in 2019 - from a ship's anchor -
Tonga signed a 15-year deal to get satellite connectivity. But the use of
satellite phones has been affected by the volcanic ash blanketing the country.
Some people have reported they can only dial out - and not receive calls. Because
of the cost, the use of satellite phones is limited to government officials,
and some businesses. Mobile network provider Digicel has set up an interim
system on the main island of Tongatapu, using the University of the South
Pacific's satellite dish to provide limited 2G coverage.
^ This was really interesting. I
knew about the cables, but not about everything it takes to build or fix on or
how many there are. Hopefully, the one on Tonga can get fixed soon. ^
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