Experimental demonstration of a 200-Gbit/s free-space optical link by multiplexing Laguerre–Gaussian beams with different radial indices

We demonstrate a 200-Gbit/s space-division multiplexing system using two Laguerre-Gaussian (LG) beams with different radial indices (LGℓ=0,p=0 and LGℓ=0,p=1). With a proper design of the radial change of the demultiplexing pattern, the channel crosstalk could be minimized and both channels could achieve a bit error rate of 3.8×10-3. Moreover, the multiplexing of four LG beams with different azimuthal indices and different radial indices (e.g., LGℓ=0,p=0, LGℓ=0,p=1, LGℓ=1,p=0, and LGℓ=1,p=1 beams) is also demonstrated with a <-12 dB channel crosstalk, potentially enabling a 400-Gbit/s data transmission.