High-resolution remote-sensing for structures and objects, using optical fibers
August 29, 2012
Optical fiber system for Brillouin optical time-domain analysis (credit: GFO, EPFL)
EPFL’s Group for Fibre Optics (GFO) has developed a technology that improves the resolution of measurements taken by optical fibers embedded in structures such as nuclear reactors, bridges, dams and buildings, or in smaller objects, providing valuable information about a structure’s heat or state of fatigue and wear.
Until now, data could be collected from points about one meter apart using optical fibers (thin glass threads) embedded in construction materials. Measurements can now be taken every centimeter —a hundredfold improvement in precision.
“Right now, we’re mainly measuring changes in temperature and force, but this method should eventually also make it possible to measure pressure variations, or even variations in magnetic field,” predicts GFO director Luc Thévenaz.
With this improvement, the fiber would be able to signal the presence of “hot spots” — weaknesses, deformations, or liquid or gas leakages — much more reliably, significantly improving the ability to monitor large structures.
The system uses “stimulated Brillouin scattering”: it sends, via laser, a beam of light trough the fiber. These waves of light generate acoustic vibrations, whose frequencies and phase change as a function of strain or temperature, allowing scientists to locate hot spots or unusual forces, with a range of tens of kilometers.
Placed in certain environments, such as underground, this optical fiber method could provide a means of detecting terrain movements or preventing the malfunction of geothermal energy installations. Placed in a glacier, it could provide information on the evolution of the snow pack.
This new technology also makes it possible to use optical fibers in smaller objects, such as robots, household appliances, or skis. It has been proposed to ride on EPFL Space Center’s “Clean Space One,” a small satellite designed for cleaning up space debris floating in near-Earth orbit.
Comments (5)
by Ian Clarke
Presumably, this technique could be used to prevent leaking water pipes. It’s a big problem in the UK. 20% of our treated water is lost in leakage – that’s enough water to serve the daily needs of approximately 22 million people!
I envision a day when these new wonder materials will start being used to address these rather basic problems.
Tarmac that won’t crack and need replacing being another example. :-)
by Editor
Yes, good idea for new infrastructure. Same for electrical, phone, and gas lines and other types of piping, and the centimeter-level precision would significantly reduce service costs and replace cruder time-domain reflectometers, etc. If the fibers could double as fiber optics for data, there would be a further economy of scale.
by Bri
The leaky pie problem is a big one. We have it bad in America, and it’s a big problem around the world. The pipes are cast iron and they had a limited life span when first installed. To replace it all would be very costly, so we wait till they break. There is a tech to line the interiors which is cost effective, but everybody is short on finance. For gas and oil companies the cost is to great not to do something. The have inspection robots that crawl through the pipes and test them more conventionally. The fiber optics has been in use for awhile now. It’s used primarily in reinforced concrete. These are complex materials that we know little about as they age. For dams , power plants and skyscrapers, it also becomes a serious issue. We don’t want them to fail catastrophically. That’s where this tech is focused. To understand the deformations that occur as it ages.
by Vin
Reminds me of the recent ‘nanoelectronic scaffold monitoring synthesized tissue’ story :D
by Guillermo
I haven’t heard of that one, link?