Infrared spectral dependencies of pulsed X-ray radiation-induced attenuation in single-mode optical fibers

We investigate the changes of optical absorption at infrared wavelengths induced by pulsed X-ray irradiation on single mode fibers. We focus on the influence of the germanium (Ge) and phosphorus (P) dopants. To do that, we characterize the changes of the radiation-induced attenuation (RIA) at 1310 nm and 1550 nm for shorter times after X-ray pulse (10^-7-10^-1s). We also measure the spectral dependence of the RIA (500-2000 nm) from 10^-1 s to several hundreds of seconds. We show that absorption bands peaking at infrared wavelengths mainly explain the RIA at 1310 nm and 1550 nm. In a Ge-doped fiber two infrared absorption bands, not previously reported in literature, are shown to substantially contribute to infrared RIA. In a P-doped fiber, the infrared RIA is explained by using the absorption bands of P-defects previously reported in literature with an un-reported absorption band peaking around 1.43 eV (FWHM=0.41 eV).