SUPER-HIGH-STRENGTH METAL-COATED LOW-HYDROXYL LOW-CHLORINE ALL-SILICAOPTICAL FIBERS

High-purity KS-4V synthetic silica developed in the Silicate Chemistry Institute of the Russian Academy of Sciences is tested as the core ma terial for radiation hardened optical fibers. Pure-silica-core fluorin e-doped-silica-cladding optical fibers with polymer (acrylate) or meta l (aluminum) coating are produced as the experimental samples. The lig ht-reflecting fluorine-doped silica cladding is synthesized by the pla sma outside deposition process. The aluminum coating technology used p rovides a very high strength of the fibers, unattainable for polymer c oatings, and expands the fiber operating range up to 400 degrees C. It is established that the metal coating application can result in the a nnealing of the drawing-induced color centers with an absorption peak at 630 nm. Post-gamma-irradiation loss spectra in KS-4V-based fibers m easured in 1-2 hours after 2 MGy irradiation at a dose rate of 8.3 Gy/ s in the spectral range 350-700 mm are discussed. The 630 mn absorptio n peak is practically absent from the post-irradiation loss spectra of aluminum-coated KS-4V-based fibers.