Fiber Optics Bring You Internet. Now They're Also Listening to Trains | Hacker News Reader

Fiber Optics Bring You Internet. Now They're Also Listening to Trains

wired.com

94 pointsisaacfrond21 comments

They can also be used to monitor powerline sag and temperature, at least in a developing product.

Full transcript of the podcast is available as well for those who prefer text.

https://www.volts.wtf/p/one-easy-way-to-boost-the-grid-upgra...

Optical fiber has been used to measure temperature in power cables for +25 years, called distributed temperature sensing

There's a lot you can do with lasers and a bit of glass. Current sensing via Faraday effect, temperature and/or strain measurement with Fiber Bragg Gratings, displacement measurement via Fabry Perot interferometry.

And also using unused telco dark fiber to listen to earthquakes in Iceland. Live video feed here: https://www.youtube.com/live/1_3NBuVrmCs?feature=shared

Cool! Here's an image [1] of an earthquake recorded on another DAS tap from an article [2] linked to in the extensive description on the livestream.

  Fig. 2. This sample data plot shows ground deformation along the fiber-optic cable deployed at Grímsvötn over about 50 seconds. A large event arrived near the middle of the cable at about 18:44:50 on this day as it propagated through the glacier. The signal observed around kilometers 10–12 of the fiber, which sat on top of the subglacial lake, oscillated with longer periods than the large event and may have been caused by bending of the ice sheet on top of the lake.

[1]: https://i0.wp.com/eos.org/wp-content/uploads/2021/12/ground-...

[2]: https://eos.org/science-updates/sensing-icelands-most-active...

When I was in school there was another research group doing distributed strain sending with fibre optics. They used an optical scattering to get spatially resolved strain along the fibre. I think it was one of several versions of the technology, I don't know if it ever took off.

IIRC this property of fiber optic cables was discovered via cicadas. Previous link on HackerNews: “Cicadas Are So Loud, Fiber Optic Cables Can ‘Hear’ Them”

https://news.ycombinator.com/item?id=38500065

Somewhat unrelated, but it will be a big year for the number of cicadas to emerge this spring, as two broods will emerge at the same time:

https://www.npr.org/2024/01/21/1225925053/billions-of-cicada...

Time to buy Indonesian sesame seed futures!

Silicon Valley was such an amazing show.

It was!

The clip I referenced, for anyone who hasn't seen it https://www.youtube.com/watch?v=KUxMY77i0q4

The property itself was always known and used for industrial purposes, the discovery was that standard network gears had improved enough and cicadas turned out loud enough that it can be done.

Hey, it's my current industry!

This would be huge, actually. Rail is incredibly capex-heavy, and moreso than many other industries, knowing well in advance when you're SIL-certified hardware is starting to run into problems is vital for procuring the right stuff to fix them - skilled labor and capital alike.

Not super relevant to what we do (we make the screens that tell you what the next stop is, so you don't have to constantly surveil the landscape) but anything which can make these lovely behemoths cheaper to operate is a win in my book.

Previous discussion [1] on a related story from WIRED [2] (2021, both).

[1]: https://news.ycombinator.com/item?id=27729402#27729935

[2]: https://www.wired.com/story/how-underground-fiber-optics-spy...

Could you do this with fibers that are also in use for communications?

It makes sense that if you tune your transmitter/receiver to squeeze absolutely as much data as you can through a fiber, the results will be very sensitive to the conditions along that fiber. So, monitoring the error rate should give you precise information about the fiber's characteristics.

Also listening for water leaks in underground pipes. https://terra15.com.au/terra15-provides-leak-detection-servi...

They bring “internet access” —- the internet is far too big to be delivered anywhere.

Hey now, just be thankful they didn't say "Wifi".

Seriously

The worst kind of pedantry is incorrect pedantry. The internet is a collection of routes, and that they most certainly do bring.

'Collection of routes' is a really intuitive description, thanks.

Reply on news.ycombinator.com