Fig. 1. (a) Schematic of the proposed sensor. Cross-sectional microscope view of (b) RCF and (c) MMF.

Fig. 2. Propagation field distribution with different structures. (a) SMF–RCF–SMF; (b) SMF–MMF–RCF–SMF; and (c) SMF–MMF–RCF–MMF–SMF.

Fig. 3. Schematic diagram of the refractive index distribution of straight and bending fibers. The inset shows simulation results of the light field distribution at Z = 6500 µm.

Fig. 4. (a) Measured transmission spectrum; (b) FFT of measured spectrum.

Fig. 5. Mode field distribution are obtained by using FEM. (a) LP₂₁; (b) LP₃₁; (c) LP₂₉.

Fig. 6. Experimental setup for the curvature measurement.

Fig. 7. (a) Interference dip (at 1450 nm) evolution with different curvatures; (b) average wavelength-bending response with error bars for four testing results; the inset shows linear fitting of the four measurements.

Fig. 8. Average intensity-bending response with error bars for four testing results; the inset shows the linear fitting of the four measurements.

Fig. 9. (a) Spectral responses under different temperatures; (b) wavelength and intensity response to temperature.