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Revolutionizing Communications With Holey Optical Fibers
 Holes less than a micron in diameter may revolutionize the fiber optics world in the next few years. Holey fibers can guide light by replacing the chemically doped cladding with a pure silica region which includes air holes. These fibers can help control the spreading of an optical pulse and even guide a single mode over all wavelengths, both important features for high data rate transmission. Holey fibers have been shown to almost entirely eliminate optical non-linearities and dispersion, and to provide exotic optical characteristics. Holey fibers are being discussed for optical switches using very low light power, sensor applications, and even low-cost fiber to the home. They are also being studied for applications such as high-powered fiber lasers, and high power delivery fibers for laser surgery and laser welding.
Until now, holey fibers have been fabricated using a complex process that requires producing a preform with precisely stacked tubes with the central tube replaced with a solid rod. When drawn under carefully controlled conditions, the holes in the tubes are preserved in the fiber. Fabrication of large numbers of holes in the optical fiber requires that large numbers of tubes be stacked and oriented in the preform. While some of the novel properties of these single material fibers depend on the precise ordering and periodicity of the holes, many do not.
Virginia Tech researchers, with funding from the Air Force Office of Scientific Research, have developed an innovative process of creating random hole optical fibers. The process generates bubbles in a powdered silica cladding, which extend to form tubules of random size, locations, and length. These resulting holes are not continuous along the length of the fiber, but there are a sufficient number of holes to provide a consistent lowering of the refractive index. Waveguide loss is similar to that of other early holey fibers. The Virginia Tech process may yield lower cost fibers, enable the use of different materials, and yield holey fibers that demonstrate behavior similar to the ordered holey fibers.
Faculty researchers on the project include: Roger Stolen, Gary Pickrell, Ahmad Safaai-Jazi, Anbo Wang.
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