Fig. 1. Gaussian fitting model and actual waveform of the FBG reflection spectrum. (a) Gaussian fitting model; (b) actual waveform

Fig. 2. Correspondence between threshold and correlation coefficient

Fig. 3. Original waveform and the waveform after noise reduction. (a) Original waveform; (b) waveform after noise reduction

Fig. 4. Flow chart of FBG wavelength demodulation algorithm based on wavelet denoising

Fig. 5. Waveform diagram of function f (x)

Fig. 6. Schematic diagram of the FBG demodulation system based on VCSEL

Fig. 7. Fitting results of wavelength and temperature

Fig. 8. Temperature of each phase of the transformer. (a) LV winding of A phase; (b) HV winding of A phase; (c) LV winding of B phase; (d) HV winding of B phase; (e) LV winding of C phase; (f) HV winding of C phase

Fig. 9. Wavelength demodulation standard deviation of different algorithms