Fig. 1. Schematic of experimental setup

Fig. 2. Schematic of light evolution in FWM generation process

Fig. 3. Reflection spectra of grating used in experiment. (a) Reflection spectrum of CFBG; (b) reflection spectrum of PM-FBG

Fig. 4. Output spectral results of experiment. (a) Output spectrum of section A; (b) output spectrum of section A within 50 min; (c) output spectrum of section B; (d) output spectrum of section B within 50 min

Fig. 5. Spectral changes in temperature rising. (a) Output spectra of sensitivity-enhancement device at different temperatures; (b) changes in wavelength difference

Fig. 6. Responses of temperature sensing. (a) Pump wavelength difference Δλp; (b) 1st-FWM wavelength difference Δλ1; (c) 2nd-FWM wavelength difference Δλ2; (d) 3rd-FWM wavelength difference Δλ3

Fig. 7. Package structure of PM-FBG

Fig. 8. Responses of output wavelength to axial strain. (a) Output spectra of system at different strains; (b) λp and λs as functions of axial strain

Fig. 9. Responses of axial strain. (a) Pump wavelength difference Δλp; (b) 3rd-FWM wavelength difference Δλ3