Synthesizing the crosstalk between OAM modes of vortex beam by simultaneously propagating a probe vortex beam in free space

•A mitigating crosstalk method is proposed by simultaneously propagating a probe beam with a data beam when the multiplexed vortex beam are propagated over a atmosphere turbulence (AT) free space.•A conjugated crosstalk is achieved by the probe beam during the square-law mixture in a photoelectric detector.•The conjugated crosstalk phase can effectively synthesize the crosstalk of data beam induced by AT.•A proof of concept is built to investigate the crosstalk, bit error rate, constellation plot, stability of system, etc. for verifying the feasibility of the proposed concept in practice.