Fig. 1. Theoretical model of FBG loop ring-down cavity

Fig. 2. Simulated results of FBG loop ring-down cavity with different temperature perturbations. (a) FBG spectral response; (b) exponential decay curve of intensity; (c) logarithm curve of intensity

Fig. 3. Temperature sensing setup of FLRDC-FBG based on FPGA

Fig. 4. Signal of optical pulse. (a) Period of optical pulse; (b) width of optical pulse

Fig. 5. Pulse ring-down waveforms and wavelength evolution at different temperatures. (a)-(d) Pulse ring-down waveforms; (e)-(h) wavelength evolution

Fig. 6. Fitting curves at different temperatures. (a) Evolution process of ring-down time; (b) relationship between temperature and (1/τ-1/τ₀)

Fig. 7. Transmission spectral evolution curves at different temperatures. (a) Transmission spectra of FBG; (b) linear relationship between Δλ and (1/τ-1/τ₀)

Fig. 8. Operation performance. (a) Repeatability results (b) stability results