Neutron Radiation Response of Optical Fiber Gratings for Sensing in Harsh Environment

Monitoring in radiation-intensive environments poses major challenges for conventional sensing technologies, which often suffer from performance degradation, high maintenance demands and limited long-term stability. In this context, optical fiber (OF) sensors represent a promising alternative. However, their deployment in such applications requires a systematic qualification of their radiation response under realistic operating conditions. In this work we report on results collected during the first neutron irradiation campaign of both bare and titanium dioxide-coated UV-written Long Period Gratings (LPGs), as well as Fiber Bragg Gratings (FBGs) inscribed by UV and femtosecond laser techniques, in photosensitive B-Ge doped fibers. The LPGs were exposed to a cumulative neutron fluence of ∼3.4 × 10¹ n/cm², while the FBGs to a higher fluence of ∼8.6 × 10¹ n/cm². The spectral response of the investigated samples under neutron irradiation was analyzed with respect to wavelength shifts and visibility variations. Collected results clearly demonstrate the robustness of OF devices in neutron environments and highlight the potential of nanoscale coatings to design radiation-hardened optical sensors. Moreover, such advances enable strategies for the development of enhanced OF sensing platforms for environmental monitoring in nuclear and high-energy physics applications.