%0 Journal Article %T Electron-Irradiation and Photo-Excitation Darkening and Bleaching of Yb Doped Silica Fibers: Comparison %A Alexander V. KirĄŻyanov %J Optics and Photonics Journal %P 155-166 %@ 2160-889X %D 2011 %I Scientific Research Publishing %R 10.4236/opj.2011.14026 %X We report a comparative experimental study of the attenuation spectra transformations for a series of Yb doped alumino-germano silicate fibers with different contents of Yb<sup>3+</sup> dopants, which arise as the result of irradiation either by a beam of high-energy electrons or by resonant (into the 977-nm absorption peak of YbYb<sup>3+</sup> ions) optical pumping. The experimental data obtained reveal that in the two circumstances, substantial and complex but different in appearance changes occur within the resonant absorption band of YbYb<sup>3+</sup> ions and in the off-resonance background loss of the fibers. Possible mechanisms responsible for these spectral changes are discussed. %K Ytterbium Doped Silica Fibers %K Photodarkening %K Electron Irradiation %U http://www.scirp.org/journal/PaperInformation.aspx?PaperID=8982