Optical Fiber Gratings Using Near-UV Light

Abstract

Abstract : Experiments were performed to elucidate the physical mechanism by which light alters the refractive index of germanium-doped optical fibers. It was found that loading the fiber with hydrogen turns on a separate physical mechanism so that all of the Ge atoms become photosensitive and not just the Ge defects. New experimental results explain the reduced stability of optical fibers and fiber gratings in the presence of hydrogen, as well as the strength of gratings written through the polymer coating of optical fibers. A method is shown for writing long period gratings in fibers with no unwanted harmonics or sidelobes. A new type of real-time fiber sensor is demonstrated that needs no spectrometer and senses either temperature or strain. In addition, a large number of specialty optical fiber gratings were fabricated in germanium-doped fibers and supplied to other research groups for demonstrations of systems applications including (a) adjustable dispersion compensators, (b) adjustable delay elements in a fiberoptic network, (c) mode-locked lasers that lase on multiple wavelengths, and (d) WDM systems that use packet headers.