Temperature-strain discrimination sensor using a WDM chirped in-fibre Bragg grating and an extrinsic Fabry-Perot

A novel fibre-optic sensing system used for temperature-strain discriminati on is presented. This system consists of an extrinsic Fabry-Perot interfero metric 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 t he CFBG induced by temperature change in the 1.55 mum region is interrogate d with an intensity-based scheme, allowing fast measurement of temperature. The cavity length change of the EFPI is measured in the 1.3 mum region, al lowing 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 degrees C, respectively.