IR absorption and spontaneous Raman scattering spectra of germanosilicate optical fibers loaded with molecular H at pressures of 150 to 170MPa, as well as the change of these spectra during H out-diffusion from the fibers were investigated. Purely rotational transitions of molecular H in the Raman spectra of optical fibers were observed for the first time. Changes in spectral characteristics of the fiber Bragg gratings subjected to H processing were analyzed. It was found that after loading at so high pressures a decrease in H concentration in the fiber core exhibits 2 different stages, the initial stage being faster as compared with that for fibers loaded at 10 to 15MPa. To explain this phenomenon, the influence of gradient of internal stress caused by H dissolved in the glass network as well as the ortho–para H conversion in germanosilicate glass were considered. An increase in solubility of molecular H in the glass network subjected to UV irradiation was revealed.

Hydrogen Diffusion and Ortho–Para Conversion in Absorption and Raman Spectra of Germanosilicate Optical Fibers Hydrogen-Loaded at 150–170MPa. V.G.Plotnichenko, S.A.Vasiliev, A.O.Rybaltovskii, V.V.Koltashev, V.O.Sokolov, S.N.Klyamkin, O.I.Medvedkov, A.A.Rybaltovskii, A.R.Malosiev, E.M.Dianov: Journal of Non-Crystalline Solids, 2005, 351[49-51], 3677-84