Fig. 1. Schematic of beam alignment of wireless optical communication. (a) Coaxial alignment; (b) two-dimensional mirror assisted alignment

Fig. 2. Geometrical optical model of two-dimensional mirror

Fig. 3. Laser tracking algorithm block diagram using two-dimensional mirror

Fig. 4. Wireless optical communication IM/DD system with fast alignment of two-dimensional mirror

Fig. 5. Schematic of field experiment of wireless optical communication for 1.3 km. (a) Link diagram; (b) far field spot

Fig. 6. Schematic of beam fast calibration. (a) Structure diagram; (b) calibration camera interface

Fig. 7. Tracking curves of calibration camera system in 1.3 km field experiment under different adjustments. (a) Pitch adjustment; (b) azimuth adjustment

Fig. 8. Trajectories of outgoing spot under different incident angles and scanning angles. (a) α＝10°，θ₁＝－1°1°，θ₂＝－5°5°；(b) α＝30°，θ₁＝－1°1°，θ₂＝－5°5°；(c) α＝10°，θ₁＝－1°1°，θ₂＝－10°10°；(d) α＝10°，θ₁＝－2°2°，θ₂＝－5°5°

Fig. 9. Power spectral density of spot center drift in 1.3 km field experiment. (a) x direction; (b) y direction

Fig. 10. Tracking waveforms in 1.3 km field experiment. (a) Tracking curve; (b) track curves along x and y directions; (c) power spectral density along x direction; (d) power spectral density along y direction

Fig. 11. Signal waveforms at 1.3 km communication link. (a) Transmitting signal; (b) receiving signal

Fig. 12. Schematic of wireless optical communication system in 10.3 km field experiment. (a) Link diagram; (b) far field spot

Fig. 13. Tracking curves detected by calibration camera in 10.3 km field experiment. (a) Pitch adjustment; (b) azimuth adjustment

Fig. 14. Bidirectional alignment schematic in 10.3 km experiment. (a) System schematic; (b) transmitting end; (c) receiving end

Fig. 15. Results of 10.3 km bidirectional alignment experiment. (a) Downlink transmission signal waveform; (b) uplink detection spot

Fig. 16. Power spectral density of spot center drift in 10.3 km field experiment. (a) x direction; (b) y direction

Fig. 17. Tracking waveforms in 10.3 km field experiment. (a) Tracking curve; (b) track curves along x and y directions; (c) power spectral density along x direction; (d) power spectral density along y direction

Fig. 18. Signal waveforms at 10.3 km communication link. (a) Transmitting signal; (b) receiving signal