Fig. 1. Brillouin scattering gain spectra

Fig. 2. Flow chart of temperature measurements based on RBFNN and fitting methods

Fig. 3. Structural diagram of RBFNN

Fig. 4. Structural diagram of Brillouin gain spectrum test system

Fig. 5. Brillouin spectra at different sweeping frequencies and at 45 ℃. (a) 1 MHz; (b) 5 MHz; (c) 10 MHz; (d) 20 MHz

Fig. 6. Smooth fitting curve of Brillouin spectrum at 45 ℃

Fig. 7. Linear fitting of Brillouin frequency shift

Fig. 8. Errors of test samples using fitting method

Fig. 9. Test errors of RBFNN and BPNN at sweeping frequency of 0.175 MHz

Fig. 10. Predicted temperature deviations at 5 different sweeping frequencies

Fig. 11. RMSEs for 3 methods at 5 different sweeping frequencies

Fig. 12. RMSEs for 3 methods after linewidth extension at 5 different sweeping frequencies