This report focuses on free-space optical (FSO) communication as a next-generation high-speed communication technology to meet the rapidly increasing demand for data traffic, and examines the challenges and solutions for its practical application. While FSO communication can achieve high-speed, large-capacity and secure communication by leveraging the straight-line propagation and wideband characteristics of light, it faces the problem of degraded communication quality due to transceiver installation errors and minute optical axis fluctuations caused by atmospheric turbulence. To address these issues, Mitsubishi Heavy Industries, Ltd. (MHI) developed acquisition and tracking technology for installation errors and optical axis compensation technology for axis fluctuations, achieving high-speed and high-precision optical axis control. Furthermore, in collaboration with NTT, Inc., which possesses optical fiber communication expertise, MHI confirmed that a maximum transmission rate of 100 Gbps can be achieved even in outdoor environments over a distance of 1 km with strong atmospheric turbulence, maintaining an average transmission rate of 93 Gbps per unit time. These results represent a significant outcome toward the practical application of FSO communication and demonstrate its potential for use in disaster-affected areas, regions with undeveloped infrastructure, and mobile-to-mobile communications.
