Fig. 1. Microscope image of the cross section of TW-GMF

Fig. 2. Simulation modeling diagram. (a) Schematic diagram of a triangular element; (b) devision of triangular mesh in FEM

Fig. 3. Mode field distributions of core mode of simulated TW-GMF at 1550 nm. (a) LP₀₁(x), n₁=1.46057; (b) LP₀₁(y), n₂=1.46055 ; (c) LP₁₁, n₃=1.45759; (d) LP₁₁, n₄=1.45754; (e) LP₁₁, n₅=1.45693; (f) LP₁₁, n₆=1.45688

Fig. 4. Refractive index curves of core mode of simulated TW-GMF. Insert is the enlarged view of refractive index curves of LP₀₁(x) and LP₀₁(y) modes

Fig. 5. Variation curve of mode loss of GMF with wavelength

Fig. 6. Schematic diagram of reflecting modal interference structure based on refractive index guided TW-GMF

Fig. 7. Image of sensor structure under microscope. Image on the right is the local magnification of fusion point

Fig. 8. Reflection spectra of GMF sensors with different lengths. (a) L=2 cm; (b) L=5 cm; (c) L=7 cm

Fig. 9. Schematic diagram of experimental setup for pressure sensing measurement

Fig. 10. Pressure sensing characteristics of GMF sensors with different lengths

Fig. 11. Response stability of GMF sensor wavelength to pressure when switching between different pressures