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

Runzhou Zhang*, Nanzhe Hu, Huibin Zhou, Kaiheng Zou, Xinzhou Su, Yiyu Zhou, Haoqian Song, Kai Pang, Hao Song, Amir Minoofar, Zhe Zhao, Cong Liu, Karapet Manukyan, Ahmed Almaiman, Brittany Lynn, Robert W. Boyd, Moshe Tur, Alan E. Willner*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


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.

Original languageEnglish
Pages (from-to)743-750
Number of pages8
JournalNature Photonics
Issue number10
StatePublished - Oct 2021


FundersFunder number
Airbus Institute for Engineering Research
Basic Research Office of the Assistant Secretary of Defense for Research and Engineering
Canada Research Chairs Program
Defense Security Cooperation AgencyDSCA 4441006051
Office of Naval ResearchN00014-16-1-2813
Multidisciplinary University Research InitiativeN00014-20-1-2558
Naval Information Warfare Center PacificN00014-17-1-2443, N6600120C4704
Natural Sciences and Engineering Research Council of Canada


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