Effect of Inner Cladding Glass Composition on Gamma-rays Response of Germano-silicate Glass Core Optical Fiber

Abstract

Recently the use of optical fiber waveguide and sensor devices based on the specialty optical fibers in radiation-harsh environments has been increasing. Since the radiationresistant property is essential, various types of radiation-resistant specialty optical fibers have been fabricated by changing the glass composition of the fiber core. But these fibers suffer from splice loss caused by difference in core glass composition and refractive index. Thus, we fabricated germano-silicate glass core optical fibers without changing the core composition but employing inner cladding of silica glasses doped with boron (B) and fluorine (F). Radiation induced attenuation (RIA) and irradiation damage recovery of the fibers were measured by irradiating the fibers with a 60 Co γ-ray at dose-rate of 19.83 Gy/min (total dose: 1.19 kGy) at room temperature. As the γ-ray irradiation increased from 0 to 1.19 kGy for 1 hour, the RIAs at 1550 nm of all the fibers increased but linearly for the fibers with B-doped and F-doped silica inner claddings and nonlinearly for the fiber with pure silica cladding. The RIAs with the dose-rate of 1.19 kGy/h became decreased after employing the inner claddings from 177 dB/km (pure silica) to 119 dB/km (B-doped), and 107 dB/km (F-doped). This linear response and lower RIAs may be due to the employed doped cladding layers, which could block the increase of non-bridging oxygen hole centers (NBOHC) and the formation of E' center before the saturation of the Ge-related defects under the γ-ray irradiation.