On the Use of Microwave Photonics Techniques for Novel Sensing Applications

The potentials of the Microwave Photonics (MWP) techniques have not been fully exploited yet by the fiber optic sensors research community. We aim to provide the use of MWP concepts for sensing under unknown schemes that can facilitate novel results under coherent regime: an interrogation technique of cascaded Fiber Bragg Gratings (FBG) sensors based on a microwave photonics filtering technique under coherent regime is presented. The sensing information of a 5-m fiber coil containing 500 weak FBG with a similar central wavelength is retrieved. The FBGs are 9-mm long and the spatial separation between consecutive FBGs is 1 mm. The principle of operation is based on the calculation of the impulse response by recording the electrical frequency response of the system. Fifteen measurements are recorded in order to average them to reduce noise and smooth the saw tooth appearance typical of coherent measurements.