Fig. 1. Coupling model of two G-lenses with Gaussian beam

Fig. 2. Transmission with errors in fiber optic rotary joints

Fig. 3. Transmission path of Gaussian beam between G-Lenses

Fig. 4. Separation misalignment，lateral offsets，angular tilt misalignment between two GRIN lenses

Fig. 5. Ray tracing in two G-Lens collimators

Fig. 6. Insertion loss curves at different $d_{\mathrm{1}}$ and $d_{\mathrm{2}}$

Fig. 7. Insertion loss curves under different errors

Fig. 8. Schematic of the principle of beam steering technology

Fig. 9. Insertion loss change diagram after optimization

Fig. 10. Experiment scheme

Fig. 11. Insertion loss of measurement and simulation with changing $d_{\mathrm{1}}$

Fig. 12. Insertion loss of G-Lens1 and G-Lens2 at different positions

Fig. 13. Insertion loss influenced by lateral offsets and separation misalignment