We know this sounds weird but in future we could ask fiber optic cables: Did the earth move for you... literally? Old, unused fiber optic cables buried underground can be refashioned into seismometers, helping scientists monitor earthquakes, according to new research. The technology to do this, known as distributed acoustic sensing (DAS), has been steadily improving over the last few years, according to a study published Wednesday in …
Carbon mics are still in use today. I have one at my elbow as I type ... it's a 1950s Model 500 Western Electric rotary dial telephone ... It still works perfectly, and is the only phone I use in my office. (Yes, my telco still supports pulse dial ... and when it drops that support, I'll install the circuitry to convert the phone to DTMF.)
As a side note, will any of the equipment you have purchased this year still work and be in daily operation 65ish years from now? I fear we are losing something very, very important in our throw-away society ...
"I fear we are losing something very, very important in our throw-away society"
Good thing you weren't around in the eighteenth century, clay pipes then were essentially single use items, pre-filled with tobacco, and thrown in the gutter once they were spent.
On the other hand, you could have joined in with people complaining about the morel degradation of the youth due to reading social media novels, and also complain about their lax and slipping standards of grammar., and generally agree that things were much better before these kids got on your lawn
Maybe you'd have fitted right in?
jake is right, there is a problem. The fact there already existed single-use items earlier in history doesn't change anything to the fact that there is no real reason a telephone (for instance) shouldn't work for decades. Its programmed death after a year or three is purely dictated by greed and is bad for everyone (except the company building the supposed replacement).
I understand that some people would rather die than be caught wearing last season's fashion, but their need for self-validation through the display of baubles others don't have acquired yet doesn't change anything. When I buy a washing machine or fridge, I expect it to last many decades, given they are simple, well-understood contraptions. For instance I definitely didn't expect an expensive, big brand washing machine to start rusting after 2 years. I thought it was long established that washing machines tend to come in contact with water, so materials would be chosen accordingly... But no, it's yet another "progress gone wrong" things: Cheap, under-specced materials make sure you'll need to buy another one in a couple years, when your previous rust bucket falls apart.
My old mother's washing machine relied on a bulky relay to work the drum back and forth. 2 quid to replace that thick chunk of copper and insulation, every 5 years. Big chunk of magnesium would prevent it from rusting. Yes, cathodic protection, on a cheap stamped steel washing machine. Clever and cheap.
New fangled stainless steel washing machine had a failed motherboard just 2 years in. $500 to replace the electronics. Straight to dumpster, pristine stainless steel drum and all.
So, not just quality of materials, but how costly to repair them over time. I'd take the chunky relay that cost 10 quid over 25 years anytime, and the single point of failure on the entire machine, besides a V-belt connecting the motor to the drum, that would usually be replaced as well, over anything more expensive and elaborate that would fail more often.
People used to REPAIR stuff, now they just CHANGE parts and bin the damaged ones. That chunky copper relay could be taken apart and rebuilt a number of times too.
(Guess what, that simple relay was common to pinball machines at one point, I later learned.)
But can they detect where the disturbance is, meaning how far down the cable ?
To me, this reads like a boolean result : the laser signal is disturbed, or it isn't. There is not enough description in the article to tell me whether the boffins knew where those 6000 perturbations were. On the other hand, they knew they had 6000 perturbations, so they must have some way of counting.
I'd like to know.
"But can they detect where the disturbance is, meaning how far down the cable ?"
Yes, you "just" measure the elapsed time between the pulse emitted by the laser and each of the reflections. The later a reflection arrives, the further away it is from the laser.
As iLurker mentioned, this principle has been applied for a number of years. One supplier is https://www.optasense.com/ A friend who has worked with this stuff mentioned that if the fibre is aboveground it can even pick up speech.
Beautiful combination of basic physics and v advanced engineering and signal processing. Makes me all weak at the knees :)
A friend who has worked with this stuff mentioned that if the fibre is aboveground it can even pick up speech.
It could even detect an approaching backhoe! Unfortunately that would a) conflict with the coding used for normal data transmissions and b) generate a lot of false positives given where operational fibre tends to get buried.
It's something that researchers have been wanting to do with subsea fibre for a long while, downside being the availability of unused and unbroken cables. Researchers have also investigated old copper cables for use as electromagnetic sensing. As you say, it's a souped up version of OTDR (Optical Time Domain Reflectometry) used to detect cable breaks and faults.
Indeed. Add some event analysis and you can do all sorts. I remember a particularly fun demo project where we buried fibre around a vehicle proving ground and then drove a rented Toyota truck around like insurgents planting IEDs. We were very relieved when the rental company actually had a Toyota one - wouldn't have been right if it wasn't! ;-)
AC as that's de rigueur for insurgents, no?
It could even detect an approaching backhoe! Unfortunately that would a) conflict with the coding used for normal data transmissions and b) generate a lot of false positives given where operational fibre tends to get buried.
Well detecting an approaching backhoe is a bit fanciful, but there's no reason this can't work with operational fiber. Almost all fiber installs include spare/dark fibers, so the sensing can be done over one of the unused fibers while the active fibers transmit data.
Even if you could detect a backhoe digging nearby, that's probably not worth much since backhoes digging nearby is not an issue, until "nearby" becomes closer than a few inches. It isn't like you would have the number of the backhoe operator and he could be called before his next bucket of dirt included your fiber!
Anything that generated large vibrations like a heavy truck driving by a fiber buried under a road or perhaps even loud thunder if enough of the vibration is transmitted through the ground to the fiber conduit, could cause the fiber bundle to shift slightly and trigger an "alarm".
Anything that generated large vibrations like a heavy truck driving by a fiber buried under a road or perhaps even loud thunder if enough of the vibration is transmitted through the ground to the fiber conduit, could cause the fiber bundle to shift slightly and trigger an "alarm".
Yup.. That's the joy of sensors. In copper, the field effects have been used for a long while for detecting things like submarines, eg along the GIUK (Greenland/Iceland/UK) gap. Same principles work for investigating the Earth's fields. Downside with subsea cables for academics is access and compatibility with the 'torpedoes' containing regen electronics along the cable.. And the old cables aren't generally maintained & break/get cut. Was pretty neat chatting with some researchers about using a transatlantic cable to investigate goings on around the mid-Atlantic rift though.
As for backhoe detection, as signal processing's got a lot better, it'd be possible to detect multiple events along a fibre, ie looking at what/where/when reflections occur. Then triangulate and monitor intensity to determine trajectory. Then pass that to a KFE (Kinetic Fault Elimination) system to prevent damage. And given man-in-the-loop systems are generally a good thing, make ops people's lives a little more interesting.
But it's cool tech, so using a grid of fibres to monitor seismic activity. Presumably with a linear sensor, you could detect/isolate more events than you can with traditional point-based seismometers.
Yes, it's a form of Time Domain Reflectometry (TDR). The electrical version has been used for ages on coaxial cable to figure out how far down the cable from the instrument a flaw(s) or a break is. The optical version (Optical Time Domain Reflectometry (OTDR)) has also been around since the dawn of fiber for the same reason - to be able to find flaws/breaks in the cable.
On the subject of boreholes...
Fibre optical cable is also increasingly used as a strain gauge in the construction industry.
Cable is attached to the reinforcement in piles and diaphragm wall panels, or fixed to the surface of existing structures, for example.
Something to do with measuring the back-scatter that occurs in the cable, which provides a reading of the strain in the cable, but also enables it to be localised (so the strain variation along the length of the cable can be measured).
There are better technical articles that predate the one referenced here.. and they don't have a paywall..
One at (dates to 2014):
https://ctemps.org/sites/ctemps.org/files/center-transformative-environmental-monitoring-programs/2014_-_parker_et_al_-_distributed_acoustic_sensing.pdf
Another:
https://eartharxiv.org/kg7q4/download&usg=AOvVaw3W7J8u7enPZ9BxwynnmXnh
google ref - they may be 'filtering'.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&cad=rja&uact=8&ved=2ahUKEwilvOeEoqDmAhXMl54KHYuzAqEQFjAJegQIBRAC&url=https%3A%2F%2Feartharxiv.org%2Fkg7q4%2Fdownload&usg=AOvVaw3W7J8u7enPZ9BxwynnmXnh
RE: Measuring rotation - Ring Laser Gyroscope
There is also something known as Fiber Optic Gyros (also a MIT project) - also known as FOGs. The Ring Laser Gyros tend to be a bit fragile(more than they claim in shock/impulse), have experience with the Honeywell HG1700 IMU. Not the quietest RLG. To avoid optical resonance lockin on the injected laser signal, the laser assembly is rapidly rotated back and forth at about 450Hz.
FOGs tend to be a bit simpler, smaller, quieter. MEMs gyros are also another interesting gyro source (least accurate of RLG and FOGs). Many commercial drones (and OTC drones) are aided by simple MEMs gyros.
Depends on the nature of the quake. During the Kaikoura 7.9 in New Zealand the earth was thrust up between 1 and 9 metres. If the road in the picture on top was the Kaikoura highway instead of cracks there would be big steps in the road. Big enough to run into or bottom out on depending on direction of travel which happened to some few on the road in the small hours.
This upthrust quake also firmly broke a LOT of communications infrastructure which too some time to fix and satellite base stations were moved in by ship and chopper to get things back up again.
The upthrust was useful in terms of rebuilding the road and rail lines as the new ways could be built over the upthrust seafloor, or alternatively they put the temporary roads there while they fixed the old one. They also took the opportunity to straighten and widen the road and build rest and viewing areas.
I know the road and rail lines well. I grew up in Auckland in the North and went to university in Dunedin in the south. Whether taking the train (Dad was a railway mechanical engineer so I got cheap fares) or on my bike (greater freedom). Much of the road is either seashore-road-rail-mountainside or seashore-rail-road-mountainside. Seals basking on the rail line are a common hazard. Those mountainsides feel down onto the ways which had been moved sideways and thrust upwards. The Kaikoura range are maritime Alps and rise directly out of the sea so I mean MOUNTAINside. It is spectacular if anyone is looking for a trip. The tourist train is back up with a special viewing car with roof windows so you can look up those mountainsides.
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