SOL-GEL DERIVED GE-DOPED SILICA GLASS FOR OPTICAL FIBER APPLICATION .2. EXCESS OPTICAL LOSS

Optical fibers of sol-gel derived germanium-doped silica core glasses are fabricated by the rod-in-tube method. Typical losses of the fibers are 20 to 30 dB/km at a wavelength in the 0.63-0.83-mu-m region. Contributions of absorption and scattering losses to the total loss of the fibers are examined. An excess absorption loss that increases with increasing germanium content is found in the optical fibers. The origin of the excess loss can be attributed to the transition metal impurities, the valence state of which is influenced by the divalent germanium ions in the fibers.