Free-Space Optical Communication System with Wide-Steering Beam for Terrestrial Access Networks

We propose a free-space optical communication (FSO) system for terrestrial access networks that features a mechanism for adjusting optical beams to a wide angle, thereby forming a network with redundant communication paths to enhance reliability. To switch optical beams precisely among multiple neighbor nodes, we utilize liquid crystal on a silicon based spatial light modulator. We report the loss characteristics of the optical beam propagating in the atmosphere near the ground and then analyze the data transfer throughput over FSO using weather condition data of Yokohama city, Japan, which features a mild climate but also heavy rainfall and a few tropical storms every year. The results showed that the FSO network was able to maintain operation without any signal power shortages for error-free services during rainy conditions for one year when it had a link length of 320 m.