Mitigating orbital angular momentum crosstalk in an optical communication uplink channel using cylindrical vector beams

The use of OAM states for multiplexing in free-space optical communications is limited by crosstalk induced by atmospheric turbulence; however, certain classes of structured beams, such as vector beams, can potentially mitigate this effect. We derive an analytical formula for the probability distribution of the orbital angular momentum (OAM) states of cylindrical vector beams (CVBs) propagating through a last kilometer optical communication uplink channel. The aperture at the receiver plane is used to reduce the turbulence-induced crosstalk from neighboring OAM states, and the effect of the turbulence parameters and choice of beam parameters on the distribution of OAM states is analyzed. Our numerical results show that by appropriately choosing the radius of the aperture, crosstalk from neighboring OAM states is significantly suppressed, while the signal OAM remains nearly invariant. Under the same conditions, we show that the signal OAM probability for a CVB is larger than that of a LG beam in over longer ranges. These results provide clear guidance for the use of CVBs in free-space optical communications.