Silica optical fibers with high oxygen excess in the core: a new type of radiation-resistant fiber

Abstract

The technology, initial properties, and the value of radiation-induced attenuation (RIA) of light in the optical communication spectral range ~1.1–1.7 μm are discussed of the novel MCVD-produced undoped-silica-core F-dopedsilica- cladding fibers, of which the core is synthesized in high O2 excess (HOE) conditions (HOE-fibers). The RIA mechanisms are analyzed and compared in the HOE-fibers and in the F-doped-silica-core fibers previously commonly considered as the most radiation-resistant. The measured RIA values in the HOE-fibers and the literature data on the RIA in the commercial radiation-resistant F-doped-silica-core fibers of Fujikura are compared at λ=1.31 and 1.55 μm. Based on this consideration, the HOE-fibers are argued to be potentially superior to the F-doped-silica-core fibers as to radiation resistance especially at long wavelengths (in particular, at λ~1.55 μm). It is also argued that the fiber drawing tension reduction can further lower RIA in the HOE-fibers. A direct experimental comparison of RIA under γ-radiation from a 60Co-source at a dose rate of 8.7 Gy/s up to a dose of 94 kGy is carried out in two HOE-fibers and a commercial radiation-resistant fiber of European make. RIA in the HOE-fibers is found to be many times lower than that in the commercial fiber throughout the optical communication spectral range ~1.1–1.7 μm.