Optical fibers typically consist of a transparent core surrounded by a transparent cladding material. The outer material has a lower index of refraction than the core material, thus trapping light in the core by internal reflection and causing the fiber to act as a waveguide.
More recently, researchers have developed hollow-core glass fibers that facilitate light transmission through the fiber—it’s easier for light to travel through air than through glass. The hollow-core fibers allow higher power transmission and reduce the need for repeaters to keep the light moving through the fiber.
Now researchers funded by the Defense Advanced Research Projects Agency and led by scientists at Honeywell Inc. have succeeded in creating hollow-core optical fibers they say allow light to travel through the fiber at approximately 99.7% the speed of light in air, a 30% improvement over silica glass optic fibers.
Adapted from ceramics.org
I have been in the field of fiber optics since early 1990s. I gained fiber optics skills and knowledge via my working experience as end-user, main contractor and sub-contractor and finally as an optical fiber enterpreneur.