28 SiO 2 -Based Isotopically Enriched Silica Fiber

— A silica fiber preform with a reflective cladding and 28 SiO 2 -based isotopically enriched core has been produced by modified chemical vapor deposition (MCVD) using high-purity 28 Si-enriched silicon tetrachloride. We have measured the refractive index profile across the preform. Using secondary ion mass spectrometry, we have obtained distribution profiles of the silicon isotopes across the preform. The 28 Si content of the silicon in the core has been determined to be at a level of 99.9%. The preform has been drawn into fiber with a reflective cladding and a 28 SiO 2 -based isotopically enriched core. The optical loss in the fiber at wavelengths from 900 to 1750 nm has been determined to be 1–2 dB/km. We have measured the radiation-induced loss in the silica fiber with the 28 SiO 2 isotopically enriched core at a gamma dose rate of 3.2 Gy/s and wavelengths of 1.31 and 1.55 μm.