Improvement of Radiation Resistance of Pure Silica Core Fibers by Hydrogen Treatment

Abstract

A pure silica core fiber with glass cladding is known to produce larger absorption in the visible wavelength region under γ-ray irradiation than a similar fiber with silicone cladding. This absorption is a serious problem, especially in image-guiding fibers used in radiation environments such as in nuclear power plants. The absorption is attributed to the formation of defect centers such as non-bridging oxygen hole centers and E' centers induced by bond scission. A new and simple method of hydrogen treatment to improve the radiation resistance of an optical fiber with a pure silica core has been proposed. Post-treatment by this method can significantly reduce existing radiation-induced absorption, while preliminary treatment can suppress the increase of the radiation-induced absorption.

Radiation-hardening techniques of dedicated optical fibres used in plasma diagnostic systems in ITER

“…Later, Nagasawa [9] observed a similar effect in irradiated glass fibres. The author observed that the hydrogen treatment, carried out either prior to or following the irradiation, drastically suppressed the 2 eV optical absorption band that develops in silica due to the formation of non-bridging oxygen hole centres (NBOHC) and Peroxy radicals (POR).…”

“…The author observed that the hydrogen treatment, carried out either prior to or following the irradiation, drastically suppressed the 2 eV optical absorption band that develops in silica due to the formation of non-bridging oxygen hole centres (NBOHC) and Peroxy radicals (POR). In 1992, Lyons and Looney [9] investigated the radiation-induced loss response at only one wavelength (850 nm) in different hydrogenated fibres. The authors explained that the combination of the pre-irradiation sequence at moderate total dose followed directly by the hydrogen loading phase contributes to reduce the number of preexisting defects and/or weak bonds that would otherwise act as precursors of colour centres during subsequent irradiation.…”

Optical characteristics of aluminum coated fused silica core fibers under 14 MeV fusion neutron irradiation

“…Optical absorption shorter than 400 nm was ascribed to E 0 center and that at 630 nm was ascribed to non-bridging oxygen hole centers (NBOHC). [8,9]. The irradiation time dependence at 400 and 630 nm is shown in Fig.…”

Study of UV fiber’s mechanical properties

“…The basic attenuation of these fibers is generally acceptable. The induced losses, primarily comes from transient or permanent changes in the silica, which are due to nonlinearities arising from two photon absorption [4].…”