Experimental Analysis of Channel Interleaving in Photon-Counting Communication over a 12-km Terrestrial Free-Space Optical Link

In lunar and deep-space optical communication uplinks, atmospheric turbulence can induce temporally correlated fades in photon-limited free-space optical (FSO) channels. These fades can lead to burst errors and consequently degrade the reliability of coded transmission. In this work, we conducted a 12 km urban horizontal free-space PPM communication experiment using a room-temperature single-photon detector. The acquired photon-counting data were used to characterize the scintillation and fade-duration statistics of the atmospheric channel. We further compared the communication performance of different channel interleaving schemes under the same link conditions. At a data rate of 25.8 Mbps, the Matrix-128 scheme achieved a receiver sensitivity of 0.86 detected photons per bit at the lowest operating point with zero observed bit errors, corresponding to a 2.64 dB sensitivity improvement over the non-interleaved scheme. The experimental results show that channel interleaving effectively disperses turbulence-induced burst errors and improves the receiver sensitivity of the high-speed photon-counting PPM system. This experiment provides field experimental evidence for evaluating the performance of channel interleaving and selecting interleaving parameters for uplink photon-counting communication under realistic atmospheric turbulence conditions.