Capacity limits of spatially multiplexed free-space communication

  • A Corrigendum to this article was published on 24 December 2015

Abstract

Increasing the information capacity per unit bandwidth has been a perennial goal of scientists and engineers1. Multiplexing of independent degrees of freedom, such as wavelength, polarization and more recently space, has been a preferred method to increase capacity2,3 in both radiofrequency and optical communication. Orbital angular momentum, a physical property of electromagnetic waves discovered recently4, has been proposed as a new degree of freedom for multiplexing to achieve capacity beyond conventional multiplexing techniques5,6,7,8,9, and has generated widespread and significant interest in the scientific community10,11,12,13,14. However, the capacity of orbital angular momentum multiplexing has not been established or compared to other multiplexing techniques. Here, we show that orbital angular momentum multiplexing is not an optimal technique for realizing the capacity limits of a free-space communication channel15,16,17 and is outperformed by both conventional line-of-sight multi-input multi-output transmission and spatial-mode multiplexing.

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Figure 1: Schematic of transmission systems.
Figure 2: Comparison of singular values of the transmission matrix in descending order for different multiplexing/demultiplexing methods.
Figure 3: Spectral efficiencies and effective degrees of freedom (EDOF) for different multiplexing/demultiplexing methods.

Change history

  • 27 November 2015

    In the version of this Letter originally published, in Fig. 3a,b, the x axis labels should have been ‘SNR (dB)’. This has now been corrected in the online versions of the Letter.

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Acknowledgements

This work was supported in part by the National Key Basic Research Program of China (973), project #2014CB340104/3, NSFC projects 61377076, 61307085 and 61431009.

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N.Z., G.L. and J.M.K. conceived and designed the theoretical model. N.Z. and X.L. performed the simulations. N.Z., G.L. and J.M.K. analysed the data. N.Z., G.L. and J.M.K. co-wrote the paper.

Corresponding authors

Correspondence to Guifang Li or Joseph M. Kahn.

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The authors declare no competing financial interests.

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Zhao, N., Li, X., Li, G. et al. Capacity limits of spatially multiplexed free-space communication. Nature Photon 9, 822–826 (2015). https://doi.org/10.1038/nphoton.2015.214

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