Electron paramagnetic resonance studies were made of low-hydroxyl synthetic silica optical fibers. These revealed the presence of a 13 G hyperfine splitting of the Si E' center which was associated with weakly bonded H molecules in the silica structure. The fibers had previously been exposed to H at room temperature. During annealing of the fibers (100C, air), the 13 G doublet declined and disappeared while the 74 G doublet and the Si E' signal grew. The results were interpreted in terms of the redistribution of H molecules, and were related to the environmental aging that occurred in fiber optical wave-guides under certain conditions.

J.Li, S.Kannan, R.L.Lehman, G.H.Sigel: Applied Physics Letters, 1995, 66[21], 2816-8