Fig. 1. Schematic diagram of QPSK satellite-ground optical communication system based on optical coherent beam combining

Fig. 2. Schematic diagram of receiving system simulation performance analysis process

Fig. 3. BER performance of satellite-ground optical communication systems with different aperture numbers at zenith angle of 45°

Fig. 4. BER performance of satellite-ground optical communication systems with different aperture numbers at zenith angle of 80°

Fig. 5. Variation of SNR with number of apertures at zenith angle of 80° and BER of 10^-7

Fig. 6. Influence of turbulence fluctuation intensity on BER under different apertures

Fig. 7. Influence of aperture receiving light power on beam combining efficiency at different zenith angles

Fig. 8. Equivalent SNR required to achieve error rate of 10^-9 for 8 aperture receiving system at different zenith angles in two situations

Fig. 9. Schematic diagram of array receiving coherent laser communication experiment

Fig. 10. Experimental device diagram of array receiving coherent laser communication. (a) Spatial optical path diagram; (b) diagram of receiving end; (c) array receiving combining beam module

Fig. 11. Schematic diagram of rotating phase screen position

Fig. 12. Flow chart of phase locking algorithm

Fig. 13. Diagrams of multi-aperture receiving array device. (a) Aperture size and layout; (b) diagram of optical path adjustment gasket

Fig. 14. Schematic diagram of optical path measurement with FMCW method

Fig. 15. Curves of output signal amplitude before and after phase-locking

Fig. 16. Spectral diagram of two communication wavelengths

Fig. 17. Constellation diagrams, eye diagrams, and spectra of transmitted signal. (a) 1550.12 nm; (b) 1551.72 nm

Fig. 18. Measured and theoretical curves of BER varying with received power in array receiving communication experiments. (a) Single wavelength, 56 Gbit/s; (b) dual wavelength, 112 Gbit/s

Fig. 19. Test result of reception availability for dual wavelength communication system