Temperature gradient measurements based on a long fiber Bragg grating and time-domain analysis

A photonic temperature sensor based on a 10 cm-long fiber Bragg grating (FBG) is presented and experimentally validated. The system is based on the measurement of the central frequency distribution of the grating based on time-frequency domain analysis. A short optical pulse is coupled into the FBG and the back-reflected pulse is scanned by means of an oscilloscope. A spatial resolution of 1 mm, given by half the input pulse duration, is achieved. The sensor proposed is based on a simply configuration and presents a sensing range of 10 cm, which could be further enhanced by fabricating a longer grating.