Inscription of fiber Bragg gratings in non photosensitive and rare earth doped fibers applying ultrafast lasers Up to now Fiber Bragg Gratings(FBG) were mainly written by absorption of an UV interference pattern inducing a periodical permanent refractive index modification in the fiber core. However this method requires the use of photosensitive fibers and is difficult to apply for the realisation of FBGs in rare earth doped fibers which is necessary for the realization of stable and robust fiber lasers. Therefore an alternative technique allowing the flexible inscription of FBGs in fibers almost independently of their chemical composition was developed based on the non linear absorption of femtosecond pulses to induce a refractive index change into the glass material.