Fig. 1. Schematic diagram of CFBG dispersion

Fig. 2. Schematic diagram of big dispersion CFBG inscription system

Fig. 3. Measurement system for big dispersion CFBG

Fig. 4. Simulation result of large dispersion CFBG. (a) Reflection spectra and transmission spectra in logarithmic scale; (b) Reflection spectra, group delay, and fitting group delay in linear scale

Fig. 5. Reflection spectra and transmission spectra of large dispersion CFBG

Fig. 6. Flow chart of wavelet threshold denoising combined with EKF algorithm

Fig. 7. Interference spectra at different central wavelengths

Fig. 8. Original signal and denoised signal with local enlarged views. (a) Original signal; (b) Denoised signal

Fig. 9. EKF tracking of interference spectrum with phase estimation, unwrapped and fitting result. (a) EKF tracking of normalized interference spectrum; (b) Wrapped and unwrapped phase; (c) Unwrapped and fitting phase

Fig. 10. Dispersion measurement results using EKF method. (a) Dispersion value at different wavelengths; (b) Dispersion measurement error

Fig. 11. Dispersion measurement results using the FT method. (a) Inverse Fourier transform and time delay correlation function; (b) Phase and fitting curve; (c) Dispersion value at different wavelengths; (d) Dispersion measurement error

Fig. 12. Dispersion measurement standard deviation using FT and EKF methods