Temperature-Strain Discrimination Sensor Using a WDM Chirped in-Fibre Bragg Grating and an Extrinsic Fabry-Pérot

A novel fibre-optic sensing system used for temperature-strain
discrimination is presented. This system consists of an extrinsic Fabry-Perot interferometric sensor (EFPI) and a chirped in-fibre Bragg grating (CFBG) in series. The EFPI and the CFBG are wavelength-division-multiplexed (WDM) to provide strain and temperature information, respectively. The wavelength-shift of the CFBG induced by temperature change in the 1.55μm region is interrogated with an intensity-based scheme, allowing fast measurement of temperature. The cavity length change of the EFPI is measured in the 1.3μm region,
allowing strain to be measured without cross-talk from the temperature sensor, i.e. the CFBG. Experimental results show that the achieved accuracies for strain and temperature measurement are ±20 x 10^-6 and ±2°C, respectively.