Demodulation technique for weakly tilted fiber Bragg grating refractometer

In this letter, a demodulation technique is presented in order to measure the surrounding refractive index in the range 1-1.45 by means of a weakly tilted fiber Bragg grating. This technique is based on the global monitoring of the cladding modes in the transmitted spectrum and on the computation of two statistical parameters. We report a resolution of 210^-4 in terms of the refractive index as well as a temperature-insensitive behavior.