Experiments of Orbital Angular Momentum Phase Properties for Long-distance Transmission

In this paper, we propose a new method to effectively measure orbital angular momentum (OAM) properties for long-distance transmission. Properties of OAM wavefront in terms of phase and amplitude are measured by rotating the OAM wave antenna and fixing the plane wave antenna as a reference. To verify OAM phase properties for long-distance transmission, experiments are conducted in Tsingtao, China, with 3.7 km and 7.0 km across the Yellow Sea, which demonstrates that vortex phase properties of OAM keep well after long-distance transmission. Meanwhile, periodical properties of OAM waves' phase fronts are the same in different transmission distances.