Improved detection of vortex superpositions in turbulence using optimal transport theory: simulations and experiments

We propose the use of orbital angular momentum (OAM) states to form modulation symbols in a free-space laser communication link affected by atmospheric turbulence. A collection of vortex superpositions with 1 to 4 active OAM states are used for transmitting digital information. Sensing and decoding data is performed with three candidate spatial detection strategies, including a Mode Sorter and a Shack-Hartmann. We use concepts of Optimal Transport, particularly the Wasserstein distance, to finding optimal selection of OAM superpositions in which turbulence is taken into account. Symbol detection and classification is performed as a whole, without the need to individually detect the OAM states. We demonstrate the effectiveness of our approach through both simulation and trials using an outdoor experimental setup.