Fiber Optics Bring You Internet. Now They're Also Listening To Trains (wired.com) 21
An anonymous reader quotes a report from Wired: Stretching thousands upon thousands of miles under your feet, a web of fibrous ears is listening. Whether you walk over buried fiber optics or drive a car across them, above-ground activity creates a characteristic vibration that ever-so-slightly disturbs the way light travels through the cables. With the right equipment, scientists can parse that disturbance to identify what the source was and when exactly it was roaming there. This quickly proliferating technique is known as distributed acoustic sensing, or DAS, and it's so sensitive that researchers recently used it to monitor the cacophony of a mass cicada emergence. Others are using the cables as an ultra-sensitive instrument for detecting volcanic eruptions and earthquakes: Unlike a traditional seismometer stuck in one place, a web of fiber optic cables can cover a whole landscape, providing unprecedented detail of Earth's rumblings at different locations. Now scientists are experimenting with bringing DAS to a railroad near you.
When a train runs along a section of track, it creates vibrations that analysts can monitor over time -- if that signal suddenly changes, it might indicate a problem with the rail, like a crack, or a snapped tie. Or if on a mountain pass a rockslide blasts across the track, DAS might "hear" that too, warning railroad operators of a problem that human eyes hadn't yet glimpsed. More gradual changes in the signal might betray the development of faults in track alignment. It just so happens that fiber optic cables already run along many railways to connect all the signaling equipment or for telecommunications. "You're utilizing the already available facilities and infrastructure for that, which can reduce the cost," says engineer Hossein Taheri, who is studying DAS for railroads at Georgia Southern University. "There could be some railroads where they don't have the fiber, and you need to lay down. But yes, most of them, usually they do already have it."
To tap into that fiber, you need a device called an interrogator, which fires laser pulses down the cables and analyzes the tiny bits of light that bounce back. So, say a rock hits the track 20 miles away from the interrogator. That creates a characteristic ground vibration that disturbs the fiber optics near the track, which shows up in the light signal. Because scientists know the speed of light, they can precisely measure the time it took for that signal to travel back to their interrogator, pinpointing the distance to the disturbance to within 10 meters, or about 30 feet. For a given stretch of track, you'd have already analyzed the DAS signals for a length of time, building a vibration profile for a normal, healthy railway. When the DAS data suddenly starts showing something different, you might have an issue, which shows up like an EKG picking up a problem with a human heartbeat. "What we're doing is profiling the track, looking for changes in the acoustic signature," says Daniel Pyke, a rail expert and spokesperson for Sensonic, which develops DAS technology for railroads. "We know what track should sound like, we know what a train should sound like. And we know that if it's changing -- so let's say this joint is coming loose -- that needs someone to go and fix it before it becomes a problem."
When a train runs along a section of track, it creates vibrations that analysts can monitor over time -- if that signal suddenly changes, it might indicate a problem with the rail, like a crack, or a snapped tie. Or if on a mountain pass a rockslide blasts across the track, DAS might "hear" that too, warning railroad operators of a problem that human eyes hadn't yet glimpsed. More gradual changes in the signal might betray the development of faults in track alignment. It just so happens that fiber optic cables already run along many railways to connect all the signaling equipment or for telecommunications. "You're utilizing the already available facilities and infrastructure for that, which can reduce the cost," says engineer Hossein Taheri, who is studying DAS for railroads at Georgia Southern University. "There could be some railroads where they don't have the fiber, and you need to lay down. But yes, most of them, usually they do already have it."
To tap into that fiber, you need a device called an interrogator, which fires laser pulses down the cables and analyzes the tiny bits of light that bounce back. So, say a rock hits the track 20 miles away from the interrogator. That creates a characteristic ground vibration that disturbs the fiber optics near the track, which shows up in the light signal. Because scientists know the speed of light, they can precisely measure the time it took for that signal to travel back to their interrogator, pinpointing the distance to the disturbance to within 10 meters, or about 30 feet. For a given stretch of track, you'd have already analyzed the DAS signals for a length of time, building a vibration profile for a normal, healthy railway. When the DAS data suddenly starts showing something different, you might have an issue, which shows up like an EKG picking up a problem with a human heartbeat. "What we're doing is profiling the track, looking for changes in the acoustic signature," says Daniel Pyke, a rail expert and spokesperson for Sensonic, which develops DAS technology for railroads. "We know what track should sound like, we know what a train should sound like. And we know that if it's changing -- so let's say this joint is coming loose -- that needs someone to go and fix it before it becomes a problem."
Thirty Year Old Tech (Score:3)
It's really weird to see WIRED writing this up now, when I was talking with some guys doing a startup in Seattle around this concept back in the '90s. It's a slightly higher-tech version of the embedded road treadles that detect your approach to a traffic signal. They were just saying to replace the capacitive or fluid pressure setups with light/lasers instead. Yard perimeter security, structures analysis in buildings and larger aircraft, and so on. Get it sensitive enough, you can use a loop of it to pick up speech on the other side of a wall.
Re: (Score:3)
Slashdot: This supposedly new product or service is just a warmed-over version of this old research.
Also Slashdot: Wake me up when this mere research becomes an actual product or service.
Re: (Score:2)
Likewise, I remember something in the 90s about cross-stitching the countryside with fibres (in peacetime) so you could detect heavy armour driving across it in war time.
The understanding of the deflection of light inside the fibre, depending on the physical condition of the fibre isn't new at all. I guess the quality of the fibre and the sensitivity of the sensors either end of it have improved to a point where it's no longer a billion dollar military project, but something you can do with (specialist) off
Re:Thirty Year Old Tech + 20 years or more (Score:1)
Trains and proactive reporting of track conditions (Score:3)
I'm not real knowledgeable about how railroads are doing things. But when I used to live and work in the DC metro area, I used to take their MARC commuter train to the office. I recall the conductor carrying a walkie-talkie and having to report in something that seemed like status of the track every so many miles? Maybe I misunderstood and it had more to do with how close they were to another train on the tracks or something like that? But it seemed like I remember hearing this computer generated voice tha
Listening in on the datacenter as well (Score:4, Informative)
Be careful what you might say inside a data center.
https://www.youtube.com/watch?... [youtube.com]
Fiber Optics Hear All (Score:4, Interesting)
What else can they hear? Trains, cicadas, earthquakes... maybe even your thoughts.
https://tech.slashdot.org/stor... [slashdot.org]
https://science.slashdot.org/s... [slashdot.org]
I can testify to that (Score:5, Interesting)
I work with optical test equipment professionally. A few of our test rigs have optical delay lines - basically big spools of single mode optical fiber between 100 m and 16 km: shoot an IR laser pulse at one end, measure it at the other end, all attenuated and elongated.
The exact way the pulse is deformed in time and amplitude depends on how exactly it bounced inside the fiber. And here's the thing: we need this deformation to be repeatable, so we can compare production devices to reference devices for QC purposes.
We actually keep the fiber spools inside a strong cabinet, itself on a thick half-inch rubber mat, because if you touch them even a little, or shake the floor too much moving heavy stuff around the room, the signal coming out of the fiber changes enough that I have to recalibrate everything, which takes a while. Even the bayonet connectors we connect fiber patch cables and test devices to the spools with are super-sensitive: look at them funny and you might have bad results.
This is all so faffy that sometimes getting all that stuff to behave is more black magic and good luck than engineering. And part of the reasons why I'm paid well is because I spent a year and a half putting it all together, and I know all the magic spells :)
Re: (Score:2)
Technology will advance when we realize the world is a chaotic place and work with it rather than conquer it.
Suure (Score:2)
You're telling me this isn't a front for using all the undersea fiber optic cables as listening devices for submarines and possibly ships too? Hmm anyway, I wonder if we still have the raw data it could be used to find the MH370 crash location.
Re: (Score:2)
Heh, yea that would be interesting, since it was hijacked by aliens and flown through a portal where it crash landed in another dimension. No, hear me out, I'm serious about this, and if it could be used to track that plane they'd hear it literally disappear from this reality.
Re: (Score:3)
I wonder if we still have the raw data it could be used to find the MH370 crash location.
If you look at a submarine cable map [submarinecablemap.com] you will find the Oman Australia Cable [wikipedia.org] is the only cable in that general area. However, it was laid in 2021, seven years after MH370.
How we've progressed (Score:1)
It never ceases to amaze me what is possible with today's technology and the scientists and engineers who develop these are capable of developing.
Within 10m, that's astonishing.
Fiber Optics brings you Internet,Stilling waiting (Score:2)
Re: Fiber Optics brings you Internet,Stilling wait (Score:4, Funny)
Maybe with this hi-tech we can finally be able to tell when the cable guy is in your driveway.
Re: (Score:2)
What I got from the summary is that this is private fiber. Owned by and used by the railroad for telemetry. Not for use by the public*.
*A local power company strung fiber many years ago. For SCADA and meter reading. They owned the poles, they had linemen with some spare time. It was cheap. And then they figured that they had so much spare bandwidth, they might as well sell it for Internet access. The telecoms screamed, pulled out their bag of dirty tricks and drove them out of a lucrative side business. Th
Re: (Score:2)
Power company is running fiber here soon so obviously it didn't work. Thanks Biden.
An interrogator walks into the staff meeting (Score:2)
Listen, Mike, we won't be needing your services at this time. But we will call you when we need you.
There was a call for you earlier. If I remember correctly, the guy's name was Saul
How? (Score:3)
A train has multiple wheels and multiple trains on a stretch of track - there will be a cacaphony of disturbances heard on the fibre - how will they know which noise aberration is from which part of the track?
Re: (Score:2)
My guess is Fourier transformation and correlation to reference data. Similar to how you can tell different voices apart when they are speaking simultaneously, plus phase information.
But that's just a guess.
It is probably a lot simpler. You cannot have too many trains at once on the same stretch of track, and you need amplifiers for long stretches of optical fibre, so it only makes sense to monitor the signals at the amplifiers, dividing the tracks into segments that are being monitored separately.