Fig. 1. Schematic of experimental setup

Fig. 2. Polarization dependent spectrum of ExTFG

Fig. 3. Sagnac loop interferometer embedded with ExTFG

Fig. 4. Schematic diagram of PMF-SI

Fig. 5. Spectrum of PMF-SI

Fig. 6. Spectral characteristics and RI sensitivity of ExTFG-SI sensor. (a) Spectral characteristics; (b) RI sensitivity

Fig. 7. Vernier spectra

Fig. 8. Vernier spectrum shift and RI sensitivity of ExTFG refractive index sensor based on VE. (a) Vernier spectrum shift;(b) RI sensitivity

Fig. 9. Analysis of temperature sensitivity. (a) Spectral evolution of TM polarized ExTFG with temperature; (b) spectral evolution of TE polarized ExTFG with temperature; (c) temperature sensitivity of ExTFG; (d) evolution of vernier spectrum with temperature; (e) temperature sensitivity of ExTFG vernier sensor

Fig. 10. Stability evaluation for ExTFG vernier sensor. (a) Five peaks chosen in vernier spectrum; (b) wavelength shift; (c) stability analysis of wavelength shift; (d) intensity change; (e) stability analysis of intensity change