Fig. 1. HC-PBF structure. (a) Electron micrograph of cross-sectional structure; (b) transmission spectrum and mode field diagrams of surface modes

Fig. 2. Simulated 7-cell HC-PBF structure. (a) Cross-section structure; (b) core surrounding structure and structural parameters

Fig. 3. Theoretical simulation results of the photonic bandgap fiber. (a) Effective refractive index dispersion curves of the fundamental mode and surface modes; (b) relationship between loss and wavelength; (c) fiber mode field at several typical wavelengths

Fig. 4. Relationship between surface scattering loss, confinement loss and temperature by theoretical calculation

Fig. 5. Sensing experimental device of HC-PBF

Fig. 6. Spectrum change of fiber under different temperatures. (a) Within 100 ℃; (b) within 300 ℃

Fig. 7. Relationship between the loss peak of the surfacemode and temperature

Fig. 8. Characteristics of strain response. (a) Change of spectra of SM2 under different strain conditions; (b) minimum transmission spectrum and the center resonance wavelength varying with strain