Experimental demonstration of free-space optical communication under 2 km urban atmosphere using adaptive fiber coupling

Satellite-to-ground communication, quantum communication, and intra-city communication all benefit from free-space optical communication. Coupling as much light power as possible into optical fibers is crucial for free-space optical communication, where atmospheric turbulence and platform sway will affect the coupling effect. This paper introduces a scheme for free-space optical communication utilizing a single adaptive fiber coupler, which can mitigate turbulence and other disturbances at minimal cost. Experimental results in a 2 km urban atmosphere show that our method can increase coupling power by up to 20% for the majority of the time. Moreover, the bit error rate of communication reduces from 4.53 × 10⁻⁴ to 3.80 × 10⁻⁸ after implementing the closed-loop correction and we also demonstrate video transmission. Additionally, this scheme can be combined with coherent beam combining and spatial diversity techniques, offering a comprehensive solution to both tip/tilt aberration and scintillation issues.