Analysis on spatial and temporal resolution in photonic time stretch frequency domain reflectometry based fully distributed fiber Bragg grating sensors

We propose and experimentally demonstrate fully distributed strain sensing along the length of a linearly chirped fibre Bragg grating with simultaneously high spatial and temporal resolution based on photonic time stretch frequency domain reflectometry (PTS-FDR). The distributed strain information is reconstructed from the instantaneous RF frequency of a temporal interference waveform via short-time Fourier transform analysis. The utility of the proposed method is characterized by analysing the spatial and temporal resolution obtained. An ultrafast strain measurement at a speed of 50 MHz with a high spatial resolution of 31.5 µm over a gauge length of 25 mm and a strain resolution of 9.1 µε have been achieved.