RADIATION-RESISTANCE OF FLUOROPHOSPHATE GLASSES FOR HIGH-PERFORMANCE OPTICAL-FIBER IN THE ULTRAVIOLET REGION

Transmission loss characteristics of a fluorophosphate fiber was inves tigated in 200-800 nm wavelength region, The transmission loss was fou nd to be primarily dominated by extrinsic absorption due to transition metal Impurities, The total scattering is the next most important los s factor which is in fact Rayleigh in character exhibiting a lambda(-4 ) dependence, and the ultraviolet absorption tail is the least signifi cant. loss factor, Radial-ion resistance characteristics of the bull; glasses corresponding to the core and cladding have also been investig ated. Upon exposure to ultraviolet radiation from a I kW HE-Xe lamp, t he radiation-induced defect centers leading to additional absorption b ands in the ultraviolet region result mainly from the photoionization processes of Fe2+ + h nu = Fe3+ + e(-) and 2Cl- + h nu = Cl- + e(-) fo r the Cl- doped glasses, and the former one is also responsible for th e glasses without doping of Cl-. The electron capture centers in the g lasses are the [PO4] and/or [P2O7] groups. If the irradiation is carri ed out with a KrF excimer laser having high-energy density, the format ion of radiation-induced defect centers is due not only to the photoio nizable multivalent ions, but also to the photoionization of phosphate groups in the glasses. The latter process gives the purple color to t he irradiated glasses. (C) 1997 American Institute of Physics.