AraOptical System and Testbed for Long-Range, High-Capacity FSOC in Rural Wireless X-Haul Networks

Long-range, high-capacity free-space optical communications (FSOC) is critical for terrestrial rural wireless x-haul and rural broadband in general. Existing terrestrial FSOC systems are however designed primarily for short-range communications. Long-range FSOC faces major challenges such as scintillation, weather, telescope misalignment, and sun noise, and there is a lack of FSOC systems and testbeds for investigating the feasibility and behavior of long-range, high-capacity terrestrial FSOC in realistic rural settings. To fill the gap, we design and implement AraOptical, a first-of-its-kind 10+ km FSOC x-haul system. We permanently deploy the AraOptical system and make it publicly available as the rural ARA testbed for empowering researchers worldwide to investigate long-range FSOC and wireless x-haul solutions. The AraOptical system features innovative designs for addressing key challenges of long-range FSOC. It effectively uses optimized COTS components such as feedback-controlled-low-noise-amplifiers and transceivers compatible with conventional routers, and it invents a novel multi-level auto-alignment algorithm tailored for the AraOptical system. The software framework of the AraOptical system features custom-designed APIs and facilitates the establishment of the ARA wireless living lab for real-world experimentation. Using the field-deployed ARA, we demonstrate, for the first time, the real-world feasibility of long-range terrestrial FSOC. AraOptical achieves a maximum throughput of 2.92 Gbps on a single channel, and, with 16 parallel channels, AraOptical is well-poised to scale to an aggregate capacity of 160 Gbps using 10G SFP+ transceivers, with potential for multi-Tbps capacity using 100G/400G coherent transceivers. We also quantitatively characterize the impact of scintillation and weather on long-range terrestrial FSOC, and we will publicly share the first-of-its-kind measurement data. The unique lessons learned from this pioneering real-world deployment of long-range FSOC systems will also facilitate future real-world studies and adoption.