Fs FBGs As Probes to Monitor Thermal Regeneration Mechanisms

This paper shows that fiber Bragg gratings written in standard single mode optical fiber with IR femtosecond pulses and point-by-point technique are high temperature resistant (<1000°C). Moreover, after calibration process, these gratings can be used as a reference to study and discriminate between different high temperature annealing mechanisms involved in other types of gratings and/or fibers. Here we have considered the regeneration process of gratings written by UV laser in boron/germanium co-doped single mode optical fiber. Hence, the monitoring of grating strength and differential wavelength shift between femtosecond and type-I gratings during annealing cycle yields the wavelength shift due to the annealing of doping (mainly boron) and UV-related defects and their relative contributions to the regeneration mechanism.