Refractive index measurement with long-period gratings arc-induced in pure-silica-core fibres

We have investigated the sensitivity of arc-induced long-period gratings to changes of ambient refractive index. Two pure-silica-core fibres with different cladding diameters and a standard fibre were used in this study. For a 6 × 10−3 change of the refractive index, a 240 pm shift of the resonant wavelength was achieved with long-period gratings written in the 125 μm cladding diameter pure-silica-core fibre.