Secure optical interconnects using orbital angular momentum beams multiplexing/multicasting

Orbital angular momentum (OAM), described by an azimuthal phase term exp ( jlθ ) , has unbound orthogonal states with different topological charges l. Therefore, with the explosive growth of global communication capacity, especially for short-distance optical interconnects, light-carrying OAM has proved its great potential to improve transmission capacity and spectral efficiency in the space-division multiplexing system due to its orthogonality, security, and compatibility with other techniques. Meanwhile, 100-m free-space optical interconnects become an alternative solution for the “last mile” problem and provide interbuilding communication. We experimentally demonstrate a 260-m secure optical interconnect using OAM multiplexing and 16-ary quadrature amplitude modulation (16-QAM) signals. We study the beam wandering, power fluctuation, channel cross talk, bit-error-rate performance, and link security. Additionally, we also investigate the link performance for 1-to-9 multicasting at the range of 260 m. Considering that the power distribution may be affected by atmospheric turbulence, we introduce an offline feedback process to make it flexibly controllable.