The characteristics of BGSM beam in atmosphere and its application in free-space optical communication

With the discussion of sixth generation gradually raising the curtain, the requirement to further expand the bandwidth makes the optical wireless communication one of the best alternatives. However, the strong atmospheric turbulence under the sunlight limits the application of the technique in the common environment. Therefore, in this paper, we study a kind of partially coherent beam (PCB), namely Bessel-Gaussian Schell-model (BGSM) beam, in terms of its propagation characteristics in atmosphere, and then construct a spacing division multiplexing (SDM) scheme based on BGSM beam. Based on the results, the BGSM beam has a stable distant annular facula that its radius is independent to the random medium, and it has wonderful atmosphere-resistance that even considering the intensity fluctuation from the PCB source, it shows larger signal-to-noise ratio (SNR) than its coherent counterpart in the strong turbulence. When several coaxial BGSM beams with different coherence distribution propagate through a space, the difference of their ring's radius makes them illuminating on different circles. Deploying the diversity reception, the source scintillation is mitigated so that every channel could afford stable transmission. Under the different turbulence condition, the SDM scheme at least double the total capacity comparing to the traditional communication scheme.