Bidirectional real-time 10-Gbit/s free-space optical link with a 4-aperture array under strong scintillation

We report on a demonstration of a bidirectional, multi-aperture free-space optics (FSO) system and discuss general system design aspects. A multi-aperture terminal is used for spatial diversity. On both sides, a real-time signal combining takes place on field-programmable gate arrays. The combined signals are weighted by their corresponding channel powers. Small form-factor C-band pluggable modules provide the opto-electrical interfaces of the 10-Gbit/s on/off-keying signals. A custom-built multi-channel bit error tester is used on both terminals for performance determination. Each aperture has an optical tracking system, is coupled to a bidirectional single-mode fiber and emits an optical power of 4 dBm.