Potential of Germano-phosphosilicate Single Mode Optical Fibers for Dosimetry

We study the Near-Infrared (NIR) Radiation-Induced Attenuation (RIA) of a Single-Mode (SM) optical fiber composed by a Ge-doped core, a ~4 μm thick P-doped inner cladding and pure Silica outer cladding. Its potential for dosimetry application has been investigated by spectral RIA measurements. The RIA, measured at 1550 nm, exhibits a linear growth as a function of the accumulated dose up to ~1 kGy(SiO ₂ ). The sensitivity to radiation, expressed by the coefficient ξ, results to be 164 mdB km ^-1 Gy ^-1 in the 0-1 kGy dose range, ~24 times lower than the one of a SM P-doped optical fiber. Furthermore, ξ almost does not depend on the dose-rate, its variation remains of the order of 6% (10 mdB km ^-1 Gy ^-1 ) for the dose-rate range from 10 mGy s ^-1 up to 10 Gy s ^-1 . At wavelengths lower than ~1450 nm, our measurements reveal a stronger dose rate dependence and less interesting dosimetric properties. Finally, a preliminary test on the 1550 nm and 1625 nm RIA at different irradiation temperatures (from room temperature to 90°C) showed no significant changes in the ξ radiation sensitivity coefficients.