4 ms·
> 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 d
by 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.