Dynamic Aperture Selection for Turbulence Resilience

Free-space optical communication systems are susceptible to atmospheric turbulence causing intermittent deep fading, which results in lost information and channel bit errors. Mitigation techniques typically require complex adaptive optics, digital signal processing or optical amplification to reduce the impact of turbulence. By spacing multiple apertures at distances comparable to the Fried parameter, spatial diversity is introduced, improving turbulence resilience. This paper demonstrates a low complexity implementation of spatial diversity, leveraging four multimode fiber coupled 1Gbps bi-directional Small Form-factor Pluggables, each near collimated by a spatially separated collection for both power combining and channel selective switching at the receiver. Under real-world turbulent conditions a sustained data rate of 1Gbps was achieved with 5.71% of frames dropped with a maximum dropout length of 0.90s over a 24-hour period. Link lengths of up to 1.3km were experimentally demonstrated.