Performance Analysis of a High-Speed PPM-SPAD System Based on Multi-Aperture Reception

To address the challenges of severe signal attenuation and weak signal detection in satellite-to-ground optical communication, this paper proposes a pulse position modulation-single photon avalanche diode (PPM-SPAD) scheme based on a single-input multiple-output (SIMO) structure. In this scheme, multiple SPAD receivers are deployed at the receiver end to mitigate the impact of the inherent dead-time characteristics of SPADs on system performance through reception diversity. A theoretical analysis framework is established in this study, and expressions for the bit error rate (BER) of the SIMO PPM-SPAD system, considering the effects of dead time, are derived. The accuracy of the theoretical analysis is validated through simulations. The simulation results demonstrate that the SIMO structure can effectively exploit reception diversity to gain significant improvement in BER performance. This research provides a solid theoretical foundation and practical guidance for the design and optimization of satellite-to-ground optical communication systems, showcasing the great potential of the SIMO PPM-SPAD scheme in enhancing system transmission performance.