Transmission behavior of silica core -: Fluorine doped cladding fibers in the visible and ultraviolet region

Pure silica core fibers with a high OH content are believed to be the best fiber type for the visible and ultaviolet region concerning low attenuation and high power stability. Here we present systematic investigations of silica core - fluorine doped cladding fibers made by MCVD, where the composition of the fiber core was slightly modified by doping with germanium, phosphorus, boron, aluminium, and fluorine at a low level of typically 0.5 mol%. Moreover, the influence of hydrogen treatment was studied. The attenuation level in the visible region, the defect band at 330 nm and the oxygen deficiency bands around 250 nm could be correlated with the preform modifications in a systematic manner. Interaction mechanisms between the defect bands and with the OH groups are discussed. The stability of the fiber against high power blue light in the Watt range was investigated. By suitably modified fibers, stability times could be realized much longer than in conventional high OH fibers.