8 ms·
Underground fiber optics spy on humans moving above
- jozvolskyef 5y ago> Because the speed of light is a known quantity, the Penn State researchers could shine a laser through a single fiber optic strand and measure vibrations at different lengths of the cable by calculating the time it took the scattered light to travel. The technique is known in geoscience as distributed acoustic sensing, or DAS. It turns out Marauder's Map was enabled by an underground array of optical cables.
- oivey 5y agoIn the electrical world, this is called time domain reflectometry.
- jleahy 5y agoIn the optical world we call it OTDR (optical time domain reflectometry). What an imaginative bunch we are /s. You can get a tiny box to do it, to find fiber breaks and bad splices.
- Prcmaker 5y agoThere's also OFDR now, frequency based. My understanding of it is pretty hand-wavey, but it's a lot more sensitive.
- canadianfella 5y ago> pretty hand-wavey What do you mean?
- shadowgovt 5y ago"hand-wavey" refers to (in this context) an understanding that is missing a lot of detail. The term refers to the notion that if someone asks you to explain a specific piece of the theory, you'd have to respond with "enhhhhh...." and a wave of your hand
- Prcmaker 5y agoYep, pretty much exactly this. I understand it enough to use it as a tool and do some rudimentary troubleshooting, but to explain how it works would require some waving of the hands to fill in my knowledge gaps.
- dustfinger 5y ago> By shining a laser through the fiber optics, the scientists could detect vibrations from above ground thanks to the way the cable ever so slightly deformed. > Civil engineers are already using DAS to study soil deformation, and biologists are even using offshore fiber optic cables to listen in on whales. (Sound propagates as a vibration, after all.) “It's just really exploding in terms of the applications,” I wonder if ISPs are using residential fiber as an optical microphone [1] array to listen to their customers? If they are not, then I could see this as a future threat. I wonder how one might inexpensively insulate a fiber-optics cable to prevent unwanted eavesdropping. [1] https://www.sciencedirect.com/science/article/abs/pii/092442479187014T https://www.sciencedirect.com/science/article/abs/pii/092442...
- binbag 5y agoPhotonics engineer here: DAS isn’t sensitive or spatially accurate enough to eavesdrop like that. Also, fibre is very rarely to the home. Normally it’s to a connection box just outside the property and then co-ax to the modem. Lastly, fibre telecoms uses lots of repeaters and switches that DAS can’t see past (needs optical line of sight).
- dustfinger 5y agoThank you for your insight, those are all great points. The fiber to my home physically runs through my home to a box that is located inside of my home. I didn't realize that most people have the box located outside of their home.
- galangalalgol 5y agoI've had fiber into an apartment and into my current home. I don't think it is that unusual.
- devit 5y agoAt least in some European countries fiber goes to a GPON terminal in the apartment and then proceeds via Ethernet cable to the home router. I'd guess the co-ax cable is probably a US-only practice.
- argomo 5y agoInteresting new use for existing tech, somewhat clickbait headline. Also, the term is "Jerry-rigged". [Edit: I stand corrected.]
- toxik 5y agoBoth are actually fine. https://www.dictionary.com/e/jury-rigged-vs-jerry-rigged/ https://www.dictionary.com/e/jury-rigged-vs-jerry-rigged/
- briefcomment 5y ago> the technology can’t exactly identify a car or person. “You can say if it's a car, or if it's a truck, or it's a bike. But you cannot say, ‘Oh, this is a Nissan Sentra, 2019,’” says Stanford University geophysicist Ariel Lellouch, who uses DAS but wasn’t involved in this study but did peer-review it. “Anonymity of DAS is one of the biggest benefits, actually.” Good.
- h4waii 5y agoI'm sure, like all people have different gait, that an acoustic profile can be matched against.
- overspeed 5y agoWith sufficient data, acoustic patterns could be learnt to identify the type of vehicle down to its model. You might be able tell it is a Sentra but not _whose_ Sentra.
- meesterdude 5y agoTrue, and with even more sufficient data, such as context and other acoustic profiling like those from the tires and one very well might be able to detect a specific Sentra.
- ska 5y ago> acoustic patterns could be learnt Maybe, but this is assuming a lot about the fundamental SNR of the measurement system, etc. It might go the other way, e.g. you can't even reliably tell it was the same vehicle twice, just a roughly similar one.
- vlovich123 5y ago> But you cannot attribute it to a specific person Until someone figures out how to do gate analysis from the data :). This is a very cool seismography technique though. Could be using fiber while it’s “dark” to perform a data gathering use for other sciences. Like a trans oceanic cable to get a new picture into our oceans with multiple data points.
- cycomanic 5y agoThere was a paper in science [1] this year looking at seismic events over a submarine link. The fibre also doesn't need to be dark in fact. [1] https://science.sciencemag.org/content/371/6532/931 https://science.sciencemag.org/content/371/6532/931
- doggodaddo78 5y agoAggregating and processing enough fiber data might be able to work towards identifying mass, contact patch size and shape, position, and velocity.
- sharikous 5y agoThat has been used 8 years ago at least to get info on Hamas tunnels across the Gaza-Israel border: https://www.timesofisrael.com/how-the-tunnels-in-gaza-are-dug-and-detected/ https://www.timesofisrael.com/how-the-tunnels-in-gaza-are-du...
- eloff 5y agoThat was an interesting read, thanks for sharing.
- fsagx 5y agoI couldn't find any links, but I remember reading about a system (or proposed system) working on this principle from the 1980s. It was meant to be deployed in the Fulda Gap region to precisely locate moving vehicles.
- Goety 5y agoAgreed, old news. Also think about apartment buildings with coax https://ieeexplore.ieee.org/document/6083650 https://ieeexplore.ieee.org/document/6083650 "Human intruder detection with Leaky Coaxial cables for wide area surveillance system" 2011 https://en.wikipedia.org/wiki/Time-domain_reflectometer https://en.wikipedia.org/wiki/Time-domain_reflectometer Paranoid memes below https://www.youtube.com/watch?v=Kr7AONv3FSg https://www.youtube.com/watch?v=Kr7AONv3FSg https://www.youtube.com/watch?v=aPMULk7AhWw https://www.youtube.com/watch?v=aPMULk7AhWw
- 71a54xd 5y agoIt's still so cool to know that in high security buildings it's common to run fiber optic comms cable inside of pipes carrying natural gas. Seems like that would largely take care of the potential for seismic eavesdropping or wiretapping haha.
- gavinheavyside 5y agoIn the mid-90's I briefly worked for a company who built and installed security systems using this principle, and it looks like they are still going: https://www.remsdaq.com/solutions/integrated-security-systems/perimeter-intrusion-detection-systems-pids/sabreline-buried-pressure-sensors/ https://www.remsdaq.com/solutions/integrated-security-system...
- peter303 5y agoStanford geophysics was the first university to run a optical fiber for studying ambient sound. Now there are dozens of these for research.
- peter303 5y agoEnergy companies like these for collecting data in harsh environments (e.g. hot geothermal wells) which would degrade conventional electronics quickly.
- rurban 5y agoAlso with magnetic influences, like thermo sensors in large transformators, breaks or motors.
- peter303 5y agoBesides acoustic waves, fiber measures strain, pressure and temperature. One proposed application is to line a water ar oil pipeline to quickly locate a leak. Currently pressure sensors every few miles. The you have to visually inspect the segment for the leak. Harder to do for buried pipelines.
- dylan604 5y agoJust look for all of the dead grasses where the spill is occurring for oil pipelines or patches of lush grasses compared to the other areas for water pipes. Or is that too simplistic?
- Prcmaker 5y agoThat indeed works, but is a time consuming manual process, pipes arent always leaking clearly (visually), and that only works when a failure has occured. I built a few fibre based instruments three or four years ago that could detect and gauge changes in the pipe caused by wall thinning (before leaks have occured), small leaks (too small to notice soil changes) and also fouling. Longevity and robustness of the sensors was always an issue though
- pottertheotter 5y agoIt's not always that easy to see. I'm on the board for my city's utilities and we recently had a leak in our 48" water main that was 380,000 gallons/day. We found out about it because of all the water coming up in someone's front yard. After repairing it and doing pressure tests, we now know we have another leak in another part of the main. However, there's all sorts of roads and other things build along the way so it's hard to know where it is, especially if it's not as big of a leak.
- Animats 5y agoThis could be a lower-cost way to do the border wall with Mexico in isolated areas. Use this to detect activity of interest, then dispatch a fast drone.
- ydlr 5y ago> then dispatch a fast drone. To do what, exactly?
- Animats 5y agoThat's a policy decision.
- atatatat 5y agoSpoken like a true defense contractor!
- mads 5y agoClearly you havent watched many Hollywood movies.
- adolph 5y agoTo zoom and enhance
- suifbwish 5y agoTo feed of course.
- throwaway74370 5y agoWith lead hopefully
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- vert1313 5y agoLooking to learn