Assessing electron radiation impact on long period gratings: radiation saturation and recovery insights

In this study, we investigate the limitations of long period gratings (LPG) by exposing them to 5.5 MeV electrons, delivering a total dose exceeding 190 kGy while the data is recorded in real time. To better understand the effects of radiation based on fiber composition, different commercially available optical fibers were selected, namely standard SMF28, B-Ge co-doped fiber, pure-silica core fiber, and P-doped fiber. To gain a deeper understanding of the advantages and limitations of using this technology in specific applications, we also examined the long-term recovery of the devices after exposure, with intermediate assessments at up to twelve months’ time. The main findings reveal that the LPG in B-Ge co-doped fiber remains responsive up to the full accumulated dose, with a resonance wavelength shift exceeding 35 nm and no signs of saturation. Furthermore, we demonstrated its potential for long-term data storage, with a 45% recovery toward initial values following post-irradiation stabilization. The novelty of this study relies in testing the limitations of LPGs fabricated both in sensitive and radiation hardened fibers while focusing on their potential i) to be reused post-irradiation and ii) to exhibit long-term data storage capabilities.