It is described a fibre optic sensor for liquid refractive index measurement based on the visibility variations of a Fabry-Perot interferometer with interfering waves generated in a short Bragg grating and in the fibre tip (Fresnel reflection) in contact with the liquid. The sensor was characterized emerging the fibre tip in distilled water with different concentrations of ethylene glycol. A linear relation was obtained, with a readout resolution of ≈ 10 -3 . It was also observed that the temperature direct cross sensitivity is residual.