Comparative Investigation of Gamma Radiation Effects on Long Period Gratings and Optical Power in Different Optical Fibers

This work presents a comparative study regarding the effects of gamma radiation on standard and different radiation hardened optical fibers, by means of arc-induced long period gratings (LPGs) written in these fibers. In particular, the resonance wavelength shift (Δλres) of LPG attenuation bands and the attenuation in the fiber transmitted optical power (ΔP) have been comparatively explored during irradiation. Different responses were observed depending on the fiber model. The Ge-doped fiber exhibits significant changes of both resonance wavelength and optical transmission loss, whereas the pure silica core fiber is mostly insensitive to radiation (Δλres and ΔP keep almost close to zero). Surprisingly, the radiation resistant fiber, with doped core, exhibits significant resonance shift even if with trivial power losses. In addition, by combining these results with numerical modeling of LPGs, we were able to estimate the radiation effects on the optical fibers under investigation, in terms of average refractive index change. These results can be useful for the application of such devices in radiation environments, i.e., for the development of both radiation sensitive and radiation hardened sensors.