Microwave photonics filtering interrogation technique under coherent regime for hot spot detection on cascaded FBG fiber

Abstract

An interrogation technique of cascaded FBGs sensors based on a Microwave Photonics filtering technique under coherent regime is presented. The sensing information of a 5m fiber coil with 500 weak FBGs with a similar central wavelength is retrieved. The principle of operation is based on the calculation of the impulsive response by recording the electrical frequency response of the system. Hot spot detection and temperature measurement are demonstrated through experimental measurements with a temperature sensitivity of 0.6dB/°C. The resolution in the measurement is related to the bandwidth of the electrical measurement and we have obtained a resolution of 20 cm for an electrical bandwidth of 1 GHz and a SNR bigger than 16dB.