Response of long period gratings to gamma and neutron-gamma radiations

Here, we report a comparative experimental investigation about the radiation sensitivity of Long Period Gratings (LPGs), fabricated in several optical fibers (from standard to radiation hardened ones) by electric arc discharge technique. For the purpose, similar set of gratings were tested under two different conditions. One is gamma radiation produced by a 60Co source using a 0.2 kGy/h dose rate and up to 25-35 kGy total doses. The other is mixed neutron-gamma exposure in a nuclear reactor at 9 Gy/s gamma-rate and 1.25â™1012 n/(cm2 â™s) neutron flux, reaching a total gamma dose of about 65 kGy and neutron fluence of 9.18â™1015 n/cm2. The analysis was focused on the real-Time radiation-induced wavelength shift exhibited by the gratings. As an outcome, the responses of the LPGs subjected to the different radiations were compared and correlated with fiber compositions.