Dark fiber optic cables as Earthquake detectors

[Oldman too]

Hello,
Recently while familiarizing myself with the rodent menace affecting Fiber optic networks, I came across this rather novel use for the dark, or unused fibers in buried cables. The method apparently holds a lot of promise as well as significant advantages over many current Seismology tools. I'm wondering if anyone is familiar with this technique, maybe @davenn or another geologically inclined individual? Thanks, Scott

Paywall version.
https://pubs.geoscienceworld.org/ss...istributed-Acoustic-Sensing-Turns-Fiber-Optic

User friendly version.
https://www.seismosoc.org/news/seismologists-see-future-in-fiber-optic-cables-as-earthquake-sensors/

https://www.seismosoc.org/news/researchers-lay-out-case-for-das-in-earthquake-early-warning/

DAS works by using the tiny internal flaws of a long optical fiber as thousands of seismic sensors along tens of kilometers of fiber optic cable. An instrument at one end sends laser pulses down a cable and collects and measures the “echo” of each pulse as it is reflected off the internal fiber flaws.

When the fiber is disturbed by changes in temperature, strain or vibrations—caused by seismic waves, for instance—there are changes in the size, frequency and phase of laser light scattered back to the DAS instrument. Seismologists can use these changes to determine the kinds of seismic waves that might have nudged the fiber, even if just by a few tens of nanometers.

 

[Baluncore]

I'm wondering if anyone is familiar with this technique,...

It is interesting, but I think it is too early to be familiar. It is still finding it's feet.

 

[Tom.G]

That's not too far fetched, there are fiber strain gauges based on a Fiber Bragg Grating.
(https://www.hbm.com/en/6827/article-how-does-an-optical-strain-gauge-actually-work/)

And sensing fibers were used on the Nine Wells Bridge near Cambridge,UK in a 2008 trial. (https://ascelibrary.org/doi/10.1061/(ASCE)BE.1943-5592.0000996)

(above found with:
https://www.google.com/search?&q=optical+fibers+bridge+strain)

Cheers,
Tom

 

[Oldman too]

A fresh paper, or at least an abstract from it. Quantum security is overlapping with Seismology.
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.180502

 

[Baluncore]

https://arxiv.org/pdf/2110.11671.pdf

 

[Oldman too]

https://arxiv.org/pdf/2110.11671.pdf

Thanks for that link, I'll post fewer abstracts now. definitely a TIL moment.

 

[Baluncore]

Thanks for that link, I'll post fewer abstracts now. definitely a TIL moment.

I used the Unpaywall extension for Firefox to find an open copy.

 

[Oldman too]

Unpaywall extension for Firefox

I'll be looking into that extension, it's new to me. Thanks for mentioning it!
(I see FF hit Version 100.0 today)

 

[Melbourne Guy]

It's not the same use case, @Oldman too, but I was at an industry conference last week and some water utilities are using fibre optics cables to detect water leaks. Apparently, our largest Telco is involved in the trial, and it utilises existing infrastructure, they are not laying any new fibre runs.

I love these "Hey, what about...?" ideas where something completely off topic is derived from existing technology. And in terms of fibre optics for earthquakes, a dedicated network is being laid on Mount Etna, so it's not existing infrastructure, but it's terrific all the same: https://www.nature.com/articles/s41467-022-29184-w

 

[Oldman too]

a dedicated network is being laid on Mount Etna, so it's not existing infrastructure, but it's terrific all the same:

That looks like a perfect neighborhood to use as a test bed, shouldn't have to wait long for data. Thanks for the Nature link, I hadn't seen it before. Here is a link to the paper it was based on, should be very interesting to see results from that network.
https://www.nature.com/articles/s41467-022-29184-w.pdf