High- temperature effects of aluminum-coated fiber

High-temperature characteristics of aluminum-coated fibers have been investigated. The fibers studied are silica core fiber and germanium-doped cored fiber. it has been found that the silica core fiber is suitable for high-temperature application, although micro-bending loss change is dominant in all aluminum-coated fiber under 100°C. Germanium-doped core fiber has shown a loss increase at high temperature due to the increase of the defect centers. The loss increase at high temperature, however, can be eliminated by high-temperature annealing because the OH diffusion at high temperature will fill up the defect centers with OH. From the investigation of the germanium concentration effects, it has been found that the density of the defect center is about ten times higher at the germanium atom site than at the silicon atom site. The Rayleigh scattering coefficient of the germanium-doped fibers has been measured and clarified in a very wide temperature range.