Multimode laser beam scintillations in weak atmospheric turbulence for vertical link laser communications

Scintillation index of multimode laser beams used for communication systems in vertical paths of weak atmospheric turbulent medium are examined by employing the Rytov method. On-axis scintillation index is examined versus the source size, propagation distance and zenith angle for vertical link including uplink and downlink. At the selected values of source sizes and propagation distances, scintillation responses of multimode laser beams are evaluated. In general, it is found for both uplink and downlink that the laser beam with multimode content has larger scintillation noise as compared to a Gaussian laser beam. However, for the downlink at L=700 km, at the chosen parameters, the multimode beam possessing larger mode content, is found to attain slightly smaller scintillations.

Automated summary

The scintillation index of multimode laser beams used in communication systems in weak atmospheric turbulent medium is examined using the Rytov method. The on-axis scintillation index is analyzed in relation to source size, propagation distance, and zenith angle for vertical links. The study finds that in general, multimode laser beams have larger scintillation noise compared to Gaussian laser beams. However, for specific parameters and at a downlink distance of 700 km, a multimode beam with larger mode content is found to have slightly smaller scintillations.