Fig. 1. Diagram of physical model of electric dipole

Fig. 2. Photonic bandgap fiber

Fig. 3. Diagram of generation of scattering secondary wave

Fig. 4. Photonic bandgap acceptance angle

Fig. 5. Focused ion beam processing technique

Fig. 6. Measuring position of AFM

Fig. 7. Two-dimensional surface topography of inner wall of photonic bandgap fiber core

Fig. 8. One-dimensional surface topography

Fig. 9. Power spectral density

Fig. 10. Fitting results of surface topography power spectral density

Fig. 11. Diagram of backscattering coefficient measurement

Fig. 12. Measurement results of backscattering coefficient