Turbulence-resilient pilot-assisted self-coherent free-space optical communications using automatic optoelectronic mixing of many modes

Abstract

In free-space optical communications that use both amplitude and phase data modulation (for example, in quadrature amplitude modulation (QAM)), the data are typically recovered by mixing a Gaussian local oscillator with a received Gaussian data beam. However, atmospheric turbulence can induce power coupling from the transmitted Gaussian mode to higher-order modes, resulting in a significantly degraded mixing efficiency and system performance. Here, we use a pilot-assisted self-coherent detection approach to overcome this problem. Specifically, we transmit both a Gaussian data beam and a frequency-offset Gaussian pilot tone beam such that both beams experience similar turbulence and modal coupling. Subsequently, a photodetector mixes all corresponding pairs of the beams’ modes. During mixing, a conjugate of the turbulence-induced modal coupling is generated and compensates the modal coupling experienced by the data, and thus the corresponding modes of the pilot and data mix efficiently. We demonstrate a 12 Gbit s−1 16-QAM polarization-multiplexed free-space optical link that is resistant to turbulence.

A Robust Basis for Multi‐Bit Optical Communication with Vectorial Light

“…The associated $$\text{BER}(N=8)\approx 2\times 10^{-3}$$ also agrees well with the fidelities reported in Figure 3c and is below the forward‐error correction limit of $$3.8\times 10^{-3}$$. [ 69–71 ]…”

“…The associated BER(N = 8) ≈ 2 × 10 −3 also agrees well with the fidelities reported in Figure 3c and is below the forwarderror correction limit of 3.8 × 10 −3 . [69][70][71]…”

Finding the superior mode basis for mode-division multiplexing: a comparison of spatial modes in air-core fiber

“…Different kinds of spatial modes also show their unique propagation properties, such as being diffraction-free, self-healing, non-line-of-sight, and turbulence-resilient 57 , 58 . Very recently, turbulence-resilient pilot-assisted self-coherent free-space optical communications using automatic optoelectronic mixing of many modes, 59 compensation-free high-dimensional free-space optical communications using turbulence-resilient vector beams, 60 and robust vectorial structured light propagation in complex media 61 have been proposed and demonstrated, showing impressive performance. In the future, more and more works are expected to find the superior mode basis for data transmission in complex media.…”

Phase memory of optical vortex beams

“…Therefore, describing the statistical properties of the phase dislocations is a topic that has received a considerable attention 34 , 40 , 43 – 49 . A few works addressed the possibility to recover the vorticity of OVs after scattering by random phase screens 50 – 53 . However, most of these reports are rather qualitative and, moreover, there is no clear description of what is meant by perturbative media such as "diffusers" or "ground glasses."…”