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Proceedings Paper

Optical communications beyond orbital angular momentum
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Paper Abstract

Current optical communication technologies are predicted to face a bandwidth capacity limit in the near future. The nature of the limitation is fundamental rather than technological and is set by nonlinearities in optical fibers. One solution, suggested over 30 years ago, comprises the use of spatial modes of light as information carriers. Along this direction, light beams endowed with orbital angular momentum (OAM) have been demonstrated as potential information carriers in both, free space and fibres. However, recent studies suggest that purely OAM modes does not increase the bandwidth of optical communication systems. In fact, in all work to date, only the azimuthal component of transverse spatial modes has been used. Crucially, all transverse spatial modes require two degrees of freedom to be described; in the context of Laguerre-Gaussian (LGp`) beams these are azimuthal (l) and radial (p), the former responsible for OAM. Here, we demonstrate a technique where both degrees of freedom of LG modes are used as information carrier over free space. We transfer images encoded using 100 spatial modes in three wavelengths as our basis, and employ a spatial demultiplexing scheme that detects all 100 modes simultaneously. Our scheme is a hybrid of MIMO and SMM, and serves as a proof-of-principle demonstration. The cross-talk between the modes is small and independent of whether OAM modes are used or not.

Paper Details

Date Published: 27 September 2016
PDF: 10 pages
Proc. SPIE 9950, Laser Beam Shaping XVII, 99500C (27 September 2016); doi: 10.1117/12.2238416
Show Author Affiliations
Carmelo Rosales-Guzmán, Univ. of the Witwatersrand (South Africa)
Abderrahmen Trichili, Univ. of Carthage (Tunisia)
Angela Dudley, Univ. of the Witwatersrand (South Africa)
CSIR National Laser Ctr. (South Africa)
Bienvenu Ndagano, Univ. of the Witwatersrand (South Africa)
Amine Ben Salem, Univ. of Carthage (Tunisia)
Mourad Zghal, Univ. of Carthage (Tunisia)
CSIR National Laser Ctr. (South Africa)
Andrew Forbes, Univ. of the Witwatersrand (South Africa)

Published in SPIE Proceedings Vol. 9950:
Laser Beam Shaping XVII
Andrew Forbes; Todd E. Lizotte, Editor(s)

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