Thermal Regeneration of Tilted Bragg Gratings UV Photo-Inscribed in Hydrogen-Loaded Standard Optical Fibers

We report on the thermal regeneration of tilted Bragg gratings (TFBGs) produced in hydrogen loaded SMF-28 optical fiber using two types of UV lasers: 266 nm femtosecond pulses and 193 nm nanosecond pulses. Different isochronal and isothermal annealing profiles are used to improve the regeneration of the cladding modes. Experimental results are in good agreement with simulation results. We show that TFBGs regenerate efficiently in the temperature range 850 °C - 900 °C when isothermal stepwise annealing profile is used. The regeneration efficiency of the cladding modes does not exceed 4.35%. The sensitivity to the surrounding refractive index is comparable to that of non-regenerated tilted Bragg gratings. These regenerated tilted Bragg gratings can be applied in several applications, like for example the follow up of high-temperature fabrication processes.