Response of long period gratings written in B/Ge and P-doped optical fibers to gamma radiation

The investigation of impact of ionizing radiation on photonic waveguides and devices is of a large interest due to new demanding applications in harsh environments, such as space or high-energy-physics experiments and more. Thus, the effects of gamma radiation on refractive index inducing propagation loss different optical fibers are investigated by means of several approaches including fiber Bragg gratings and long period gratings (LPG). In this work, we report the results on exposure to gamma irradiation up to tens of kGy of LPGs written in single-mode optical fibers with unconventional dopants, such as B and P. The LPGs in a reflective configuration have been written using the electric arc discharge technique. The attention is focused on the real-time measurement of LPG resonance, i.e., wavelength shift and transmission power changes during irradiation, as well as the recovery effects after the irradiation. It has been found that the impact of gamma is significantly dependent on the fiber type and the LPG properties. The LPGs in B/Ge co-doped fiber show both the higher resonant wavelength shift and low power losses. Such results are useful for those working with optical fibers and related sensors in environments exposed to radiations.