Abstract
Multiplexing multiple orbital angular momentum (OAM) channels enables high-capacity optical communication. However, optical scattering from ambient microparticles in the atmosphere or mode coupling in optical fibers significantly decreases the orthogonality between OAM channels for demultiplexing and eventually increases crosstalk in communication. Here, we propose a novel scattering-matrix-assisted retrieval technique (SMART) to demultiplex OAM channels from highly scattered optical fields and achieve an experimental crosstalk of –13.8 dB in the parallel sorting of 24 OAM channels after passing through a scattering medium. The SMART is implemented in a self-built data transmission system that employs a digital micromirror device to encode OAM channels and realize reference-free calibration simultaneously, thereby enabling a high tolerance to misalignment. We successfully demonstrate high-fidelity transmission of both gray and color images under scattering conditions at an error rate of <0.08%. This technique might open the door to high-performance optical communication in turbulent environments.
Highlights
Light is one of the main carriers of information in communication
The orbital angular momentum (OAM) of light has been considered as a promising degree of freedom for multiplexing data in free space[4,5,6] and optical fibers[7,8] and at the nanoscale[9,10,11,12,13]
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Summary
Light is one of the main carriers of information in communication. Fully enhancing the informationcarrying capacity and spectral efficiency of light has always been a perennial goal in both academia and industry, and it is traditionally realized by multiplexing the wavelength[1], polarization[2], and spatial degree of freedom[3] of light to increase the data channels for a parallel transformation. The orbital angular momentum (OAM) of light has been considered as a promising degree of freedom for multiplexing data in free space[4,5,6] and optical fibers[7,8] and at the nanoscale[9,10,11,12,13]. Superior to spin angular momentum (i.e., circular polarization) with two states, OAM could offer unlimited channels for data transmission. Due to this unique property, OAM multiplexing has been widely applied to achieve high-capacity communication in free space[15,16,17] and optical fibers[7,8]. Optical free-space communication using OAM multiplexing inevitably suffers from the issue of multiple scattering from ambient microparticles in the atmosphere[18,19,20], which will scramble the wavefronts of the OAM modes and destroy the orthogonality between the OAM channels[18,21]
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