Fig. 1. Schematic of quarter-wave plate. (a) Fusion of two sections HBFs; (b) testing system based on the Hi-Bi FLM

Fig. 2. Numerical curves of normalized transmissivity of Hi-Bi FLM. (a) Δφ=-π; (b) Δφ=π; (c) Δφ=-3π/2; (d) Δφ=-π/2; (e) Δφ=π/2; (f) Δφ=3π/2

Fig. 3. Schematic of experimental measurement system

Fig. 4. Transmissivity curves of the fiber loop with different positions on 2D translation stage. (a) 0 mm; (b) 0.035 mm; (c) 0.075 mm; (d) 0.145 mm; (e) 0.190 mm; (f) 0.215 mm