Jason Moore has worked at NASA Langley since 1995. He currently tests and develops fiber optic technologies, including multicore fibers. He is actively organizing ground and flight tests to demonstrate the multicore fiber’s ability to sense structural shape changes in flight.
NASA Tech Briefs: How are multicore fibers used to sense shape?
Jason Moore: Fiber optics sensors are being used for sensing everything from chemicals, to temperature, to pressure, to structural loads, and lately, structural shape. The idea with a multicore fiber is that you secure this fiber — you might tape it down or bond it — and if whatever it’s secured to bends, the fiber bends. You basically track the bending and the changing shape of the fiber, and that will directly tell what the shape of the structure is that it is secured to.
NTB: What are some of the limitations of previous fiber optic shape measurement tools?
Moore: We traditionally relied on bonding fiber optic strain sensors. That’s okay for stiff structures, but when you start getting into very flexible structures like inflatable vehicles or very flexible control surfaces and morphing flaps, having sensors bonded to such materials is just not practical. So having multicore fibers that don’t really need to be bonded — just held in place some way — has really opened the doors into doing some fiber optic shape sensing on the very flexible structures.
NTB: How is the multicore fiber being used?
Moore: The many cores are usually spaced equally throughout the fiber, in the angular sense and the radial sense. Each core is treated like an individual sensor run, and there are fiber Bragg gratings in every core, co-located down the fiber. At the micro level, a bend in the fiber will actually compress some of the cores, and they will stretch some of the other cores.
A real simple way to think about it is like a garden hose. If you had a fiber running on the inside of a bend, that fiber would get compressed, so we would be measuring negative strain using a fiber Bragg grating. If you had a fiber on the outside of the garden hose, on the outside of the bend, that fiber would get stretched; we would see positive strain measurements on that fiber Bragg grating. So with many cores, we take up the measurements from all the gratings at each individual section down the fiber and get bend measurements. From those bend measurements, there’s more math that can kick out an actual three-dimensional shape of the fiber.
NTB: What are some of the applications for this technology?
Moore: Beyond the airframe, within NASA, we’re looking at control surface shape for feedback for things like flutter suppression for very flexible flaps. Outside of NASA, I know a lot of medical folks are very excited about the possibilities of using fiber optic shape sensors inside surgical catheters for very precise surgical maneuvers inside the human body; in particular, in cases where patients may have to traditionally experience x-rays to know where surgical catheters are. I think they’re very excited about maybe eliminating many of these x-rays when they have a catheter that actually gives them the position with the accuracy they need.
To learn more about multicore fiber optic sense shaping, read a full transcript, or listen to a downloadable podcast, visit www.techbriefs.com/podcast.
Want to learn more?
On October 16, Jason Moore will lead a live webcast on multicore fiber optic technology. Go to www.techbriefs.com/webinar245 to register for the free presentation.