Turbulence-Resilient Reflective Fi-Wi-Fi Bridge for Terrestrial Free-Space Optical Data Links

Free-space optical (FSO) links enable a seamless extension of the fiber-grade bandwidth continuum in fiber-scarce environments. Towards this, we present a bidirectional fiber-wireless-fiber link that bridges the gap between two single-mode fiber ports. We utilize simple focal plane array beamformers that host 91 antenna elements on a fiber tip to ensure the optimal coupling of light in terrestrial point-to-point FSO links, for which hybrid space / wavelength-switched beamforming networks are employed to enable centralized control. The asymmetric complexity distribution in the FSO link layout is further enhanced through a reflective, source-less tail-end equipment and wavelength re-use to accomplish full-duplex 10 Gb/s data transmission with simultaneous channel sounding in an adjacent waveband. Moreover, we propose and demonstrate a graceful migration path towards diversity reception through simple wavelength-set coding, which enables us to mitigate the effect of turbulence-induced signal fading on the data transmission.