Demonstration of a 4.2km MISO free-space optical communication link using COTS SFP+ transceivers

We report the design and field testing of a retroreflector-based multiple-input single-output (MISO) free-space optical communication (FSOC) link employing commercial off-the-shelf transceivers. A four-transmitter architecture operating in the C-band is demonstrated over a 4.2 km round-trip optical path, achieving a sustained TCP throughput of 8.43 Gbps. The system incorporates optical amplification and a beacon-assisted multi-level auto-alignment scheme to mitigate link loss, misalignment, and atmospheric turbulence. Long-duration measurements are performed to experimentally characterize throughput performance and turbulence-induced power fluctuations under real outdoor conditions.