ELECTRON-PARAMAGNETIC-RESONANCE CHARACTERIZATION OF NONUNIFORM DISTRIBUTION OF HYDROGEN IN SILICA OPTICAL FIBERS

The hydrogen distribution within low-OH silica optical fibers has been characterized by electron paramagnetic resonance in combination with a chemical etch-back technique. The 74 G doublet, the signal generated by a hydrogen hyperfine structure of the Si E' center, was used to in vestigate the spatial distribution of hydrogen reaction products in si lica optical fiber and, in particular, the reaction between the twofol d coordinated silicon and hydrogen. A nonuniform distribution of the 7 4 G species was observed with the highest concentration near the fiber surface, indicative of a corresponding nonuniform distribution of hyd rogen. The polymer fiber coating appears to be the primary source of t he trace amounts of hydrogen observed in the silica fibers. (C) 1996 A merican Institute of Physics.