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