New fiber-based sensor could quickly detect structural problems in bridges and dams. Today, there is great interest in using distributed sensors to continually monitor the structural health of large structures such as dams or bridges. With 1 million sensing points, a newly developed fiber optic distributed sensor could offer significantly faster detection of structural problems than is currently available.
“With fiber-based sensors, it is possible to precisely detect erosion or cracking before a dam fails, for example,” said Alejandro Dominguez-Lopez from the University of Alcala (UAH) in Spain, from the r research team that developed the new sensor. “Earlier detection of a problem means it might be possible to prevent it from getting worse or could provide more time for evacuation.”
Fiber optic distributed sensors are ideal for monitoring infrastructure because they can be used in harsh environments and in areas that lack a nearby power supply. If a single fiber is placed along the length of a bridge, for example, changes in the structure at any of the sensing points along the optical fiber will cause detectable changes in the light traveling down the fiber. Although the popularity of fiber optic distributed sensors is growing, they are currently used primarily to detect leaks in oil pipes and to monitor for landslides along railroads.
In The Optical Society (OSA) journal Optics Letters, Dominguez-Lopez and his colleagues from UAH and the Swiss Federal Institute of Technology (EPFL) report the first fiber optic distributed sensor that can sense strain and temperature changes from 1 million sensing points over a 10-kilometer optical fiber in less than 20 minutes. Strain, which is a measure of deformation, indicates how much mechanical stress is on an object or structure.
The new sensor is about 4.5 times faster than previously reported sensors with 1 million sensing points. Although there isn’t a magic number, more sensing points means fewer fiber-optic units are needed to monitor an entire structure. This simplifies the overall sensing scheme and could potentially reduce costs.
“Because we have such a large density of sensing points—one per centimeter—our optimized sensor could also be used for monitoring in applications such as avionics and aerospace, where it’s important to know what is happening in every inch of a plane wing, for example,” said Dominguez-Lopez.