Free space-optical communication utilizing
orbital angular momentum (OAM)
multiplexing offers an extremely high transmission capacity and speed.
However, atmospheric turbulence causes mode crosstalk and power loss
during the OAM decoding. Although conventional adaptive optics (AO)
compensates the distortions, it introduces significant complexity and
cost due to the need for a wavefront sensor. This paper proposes what
we believe to be a novel sensor-less AO framework based on the
image-to-image translation capability of pix-to-pix generative
adversarial networks (pix2pixGAN). This approach directly recovers the
compensation information by recognizing the distorted image.
Laboratory experiments revealed that the proposed AO method
effectively compensates the distortions of vortex beams in the 80
Gbit/s communication system combining four wavelengths and two OAMs.
Even in severe turbulence (D/r0=8), the power sensitivity was minimally
enhanced 3.7 dBm under the bit error rate of 1∗10−3.