Effects of radiodarkening on the light transmission properties of ytterbium-doped optical fibers

Abstract

Optical fibers have been acting in a very crucial role in telecommunication and non-telecom industries like medicine, machining, sensing as well as in lasers and amplifiers when they are doped with rare earth ions for their remarkable features such as very good beam quality, high power generation and low cost after the fab-rication of first low-loss optical fibers in early 1970s. However, these outstanding properties are deteriorated when optical fibers are exposed to ionizing radiation limiting their use in nuclear power plants and space applications. The main fabrication method of silica optical fibers, Modified Chemical Vapor Deposition (MCVD), as well as the effects of compositional variations of optical fibers on the gamma radiation resistance were highlighted by this thesis. Optically sound and robust fibers were evaluated through optical and chemical characterization methods and the light guiding abilities of them were measured before and after gamma radiation exposure to reveal its effects. Ytterbium-doped silica optical fibers showed significant transmission losses due to the creation of color centers by ionizing radiation exposure which were characterized and their contribution to radiation induced attenuation was described. Growth and recovery of these color centers at room temperature were analysed. Suggestions in terms of chem-ical composition for the fabrication of radiation resistant fibers as well as fiber dosimeters were made. The techniques that should be utilized for further recovery of the fibers were proposed.