640 Gbit/s FSO turbulence-resilient field trial utilizing the cylindrical vector beam

Free-space optical (FSO) communication has the advantages of large bandwidth and high security and being license-free, making it the preferred solution for addressing the "last kilometer" of information transmission. However, it is susceptible to fluctuations in the received optical power (ROP) due to atmospheric turbulence and pointing errors, resulting in the inevitable free-space optical communication transmission performance degradation. In this work, we experimentally verified the turbulence resistance of the cylindrical vector beam (CVB) over a 3 km long free-space field trial link. A transmission capacity of 640 Gbit/s was conducted by utilizing a 20 GBaud 16-quadrature amplitude modulation (16QAM) through eight-wavelength multiplexing. The experimental results show that the CVB exhibits stronger turbulence resilience compared to the scalar circularly polarized Gaussian beam. Under moderately strong turbulence conditions, the communication stability probability of the first-order CVB improves by about 1/3 compared to the Gaussian beam, while for that of the second-order, the CVB is improved by about 1/5.