UV-induced reaction of H2 with germanosilicate and aluminosilicate glasses

The cores of optical fiber preforms were exposed to UV light at 244 nm after molecular hydrogen loading under high pressure. The reactions between hydrogen and the core material were investigated by Fourier transform infrared spectroscopy in the 3 mu m spectral range. Various glass compositions were considered: germanosilicate glasses codoped with B, Sn, or not and aluminosilicate glasses codoped with Ce or Tb. In germanosilicate glasses (codoped or not), H-2 reacts at the Ge sites only. The major defect formed is Ge-OH, some Ge-H is detected too, but at a much smaller level. In the Ce-doped aluminosilicate plates, H-2 reacts with Ce and forms Ce-OH. All these materials are reduced through the UV light exposure as shown by the presence of molecular water formed by reaction of H-2 With the glass network. The exceptions are with the Tb aluminosilicate preforms which show no reaction with H-2 under UV exposure. (C) 1998 Elsevier Science B.V.