Fig. 1. Schematic of polarization alignment of PMF. (a) Axis-fixed process; (b) axis-fixed system

Fig. 2. Front-back creeping phenomenon of end face during fiber rotation

Fig. 3. Transformation of coordinate system. (a) Original image; (b) transformed image

Fig. 4. Coordinate transformation of actual image. (a) Original image; (b) transformed image

Fig. 5. Steps for symmetry evaluation (θ=l)

Fig. 6. Schematic of steps for pyramid searching

Fig. 7. Actual image of fiber end face

Fig. 8. Six groups of simulated image samples. (a) Group A; (b) group B; (c) group C; (d) group D; (e) group E; (f) group F

Fig. 9. Detection results of six groups of images

Fig. 10. Detection results for two algorithms under different lighting conditions. (a) Good lighting condition; (b) medium lighting condition; (c) poor lighting condition

Fig. 11. Detection results for two algorithms under different defocus distances. (a) 20 μm; (b) 40 μm; (c) 60 μm