Formation and disappearance of defect centers in GeO₂-doped silica fibers with heat treatments

Electronic state changes of defect centers in Ge-doped SiO2fibers were investigated using ESR technique. The germanium associated defects, especially Ge(3) centers, are mainly produced during the drawing process and are quenched in the fibers. The heat treatment of the Ge-doped fiber causes a remarkable decrease in the Ge(3) ESR intensity, subsequently causing OH absorption loss increase. The mechanism of this OH loss increase is proposed, in relation to the interactions between the Ge(3) centers and hydrogen.