Comparative Study of Long-Period Gratings Written in Standard and Fluorine-Doped Fibers by Electric Arc Discharge

In this paper, we present a comparative study of long-period gratings (LPGs) written in the standard Ge-doped fiber and in two different fluorine-doped fibers by means of the electric arc discharge (EAD)-based technique. Concerning Ge-doped fibers, we present an assessment of the EAD procedure by fabricating relatively short LPGs with deep attenuation bands (up to 32 dB) and trivial power losses. We also demonstrate the ability to manage the effect of the single EAD perturbation to select grating length, which in turn acts on the bandwidth of attenuation bands, without compromising depth. Furthermore, for the first time, we produced LPGs in F-doped fibers with attenuation bands deeper than 30 dB, demonstrating the dependence of the spectra on the grating period. Finally, we illustrate a comparative experimental study on the sensitivity of LPGs fabricated in the standard and F-doped fibers with surrounding refractive index (SRI) and temperature changes. We proved that the SRI response of LPGs in F-doped fibers is significantly higher than in the standard fiber and it strongly depends on the type of F-doped fiber considered. LPGs written in F-doped fibers exhibit a slightly lower temperature sensitivity (in the range 20-30 pm/°C for λres2 cladding mode) than the LPG in the standard fiber (45 pm/°C).