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Comment by C14L | Hacker News Reader

On 2006-12-26 there was an underwater earthquake in Taiwan that cut off all sea cables between East Asia and Europe.

I was in China at the time. All internet traffic was going the other way around the globe and was extremely slow or most often just timed out.

It took weeks to get normal internet speeds again.

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Underwater volcanoes (rock slides) are the biggest threat to cables when you get into the deep ocean. The cables are much more thin (less armoring then when near the shore). The other fault encountered in the deep (no anchor risk) is from amplifiers failing on the cable which is a long process to get a ship out to replace.

what are you talking about here, guitar amplifiers? some radar equipment falling from a ship? optical signal amplifiers?

EDFA's: erbium doped fiber amplifier. They're optical signal amplifiers. Due to the attenuation of the fiber, they need to be installed every so often on the fiber, under the sea. Since the equipment is cheap in comparison to the cost of repair, modern undersea amplifier boxes often contain multiple amplifiers and switchgear to MUX to a new one after it fails.

This. If you see the oceanic cables every x amount of kilometers you'll see a bump in them: that's the amplifier. There are also junction points too where cables can split off to serve locations on the route. Newer cables have the ability to dynamically reconfigure these (wavelength switching) these junctions rather than be static (the older way).

very interesting, thanks both. I'm surprised something travelling at the speed of light over a relatively short distance attenuates at all. I wonder if these amplifiers are purely optical (like mini magnifying glasses), or if they are powered (requiring running adjacent power cables)

Wikipedia has a lot of details about how the amplifiers work: https://en.wikipedia.org/wiki/Submarine_communications_cable...

It’s traveling through glass and the glass has imperfections. Can you imagine trying to see through glass 30 miles thick?

Power is involved too. When I first visited a cable landing station I got to learn about the process to de-energize / energize the cable and coordinate with the ship and the remote side. Pretty involved but really neat to see. The stories are interesting too. One cable landing station on a small island the main tech would bring his family in during a typhoon to shelter there for days since it was a fairly protected site that had plenty of fuel for the generators.

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