Time Delay Measurements as Promising Technique for Tilted Fiber Bragg Grating Sensors Interrogation

A novel interrogation technique for tilted fiber Bragg gratings (TFBGs) sensors based on single wavelength time delay measurements is presented. To this aim, the group delay of a weakly TFBG has been characterized by direct time-domain measurement. The experimental characterization shows the capability of TFBGs to speed up and slow down the propagation velocity of an optical pulse in optical fiber. These sharp group delay features of the TFBGs are exploited for refractometric applications to detect the surrounding refractive index (SRI) variations by single wavelength time delay measurements. The obtained results demonstrate the possibility to detect SRI changes by means of single wavelength time delay measurements with enhanced sensitivity in the range 1.33-1.40 with respect to previously reported interrogation techniques.