Global atmospheric propagation comparison of terahertz and free-space optical communications

Abstract

Growing wireless traffic demands new spectrum for high-capacity links. This paper compares terahertz (THz, 220 GHz) and free-space optical (FSO, 1550 nm) propagation, evaluating molecular absorption, hydrometeor effects, and turbulence within a global framework combining meteorological data and propagation models. The two technologies exhibit complementary sensitivities: FSO achieves negligible molecular absorption and, under median conditions, experiences lower loss across 65% of land, while THz tolerates fog (below 6 dB/km versus 80–340 dB/km for FSO) and turbulence far more effectively. Under the same conditions, THz shows lower combined loss across 73% of Earth’s surface. For high-availability links, at a 20 dB loss margin THz keeps combined molecular and cloud loss within margin over 99% of the time across 86% of Earth’s surface, versus 2% for FSO. These complementary characteristics motivate hybrid THz-FSO architectures for future networks.