Characterization of multi-level digital waveforms for low-Earth-orbit free space optical communication

摘要

As satellite constellations continue to expand and capacity demands grow, free-space optical (FSO) communication offers a complementary alternative to RF systems for low-Earth-orbit (LEO) satellite communication networks. FSO systems can support higher link bandwidths and provide high data security without RF spectral constraints. The performance of FSO-LEO links, however, can be significantly impacted by receive power variation caused by propagation and scattering losses along with losses due to atmospheric turbulence. These loss mechanisms are not only dynamically changing during an FSO-LEO pass, but they impact link performance at different time scales. Signal power variation due to propagation and scattering losses occurs over a timescale of minutes while atmospheric turbulence impacts signal power on a millisecond timescale. Here, we investigate intensity modulated, direct detection (IM/DD) digital waveforms that can be adapted to dynamically changing link conditions to optimize bandwidth utilization. Using a laboratory scintillation playback system, the performance of BPSK, QPSK, 8PSK, 16APSK, and 16-QAM waveforms are presented.