Influence of the fiber coating on the proton radiation sensitivity of Fiber Bragg Gratings

We report on the effect of the fiber coating on the radiation sensitivity of Fiber Bragg Gratings (FBG). For the first time this type of study has been carried out using a 13.5 MeV proton beam up to a fluence of 3.3 × 10¹⁵ protons/cm² (total absorbed dose of 15 MGy). We observed a clear dependence of the radiation sensitivity on the coating, in particular, we have investigated the irradiation induced changes on the strain sensitivity; FBG strain coefficient remains stable for all the fiber within a 5%. This result demonstrates the suitability of FBGs as displacement transducers in the very hostile environment of the new generation of high-intensity particle physics proton colliders.