83 research outputs found
Orbital Angular Momentum-based Space Division Multiplexing for High-capacity Underwater Optical Communications
To increase system capacity of underwater optical communications, we employ
the spatial domain to simultaneously transmit multiple orthogonal spatial
beams, each carrying an independent data channel. In this paper, we multiplex
and transmit four green orbital angular momentum (OAM) beams through a single
aperture. Moreover, we investigate the degrading effects of
scattering/turbidity, water current, and thermal gradient-induced turbulence,
and we find that thermal gradients cause the most distortions and turbidity
causes the most loss. We show systems results using two different data
generation techniques, one at 1064 nm for 10-Gbit/s/beam and one at 520 nm for
1-Gbit/s/beam, we use both techniques since present data-modulation
technologies are faster for infrared (IR) than for green. For the higher-rate
link, data is modulated in the IR, and OAM imprinting is performed in the green
using a specially-designed metasurface phase mask. For the lower rates, a green
laser diode is directly modulated. Finally, we show that inter-channel
crosstalk induced by thermal gradients can be mitigated using multi-channel
equalisation processing.Comment: 26 pages, 5 figure
Efficient Multi-Pair IoT Communication with Holographically Enhanced Meta-Surfaces Leveraging OAM Beams: Bridging Theory and Prototype
Meta-surfaces, also known as Reconfigurable Intelligent Surfaces (RIS), have
emerged as a cost-effective, low power consumption, and flexible solution for
enabling multiple applications in Internet of Things (IoT). However, in the
context of meta-surface-assisted multi-pair IoT communications, significant
interference issues often arise amount multiple channels. This issue is
particularly pronounced in scenarios characterized by Line-of-Sight (LoS)
conditions, where the channels exhibit low rank due to the significant
correlation in propagation paths. These challenges pose a considerable threat
to the quality of communication when multiplexing data streams. In this paper,
we introduce a meta-surface-aided communication scheme for multi-pair
interactions in IoT environments. Inspired by holographic technology, a novel
compensation method on the whole meta-surface has been proposed, which allows
for independent multi-pair direct data streams transmission with low
interference. To further reduce correlation under LoS channel conditions, we
propose a vortex beam-based solution that leverages the low correlation
property between distinct topological modes. We use different vortex beams to
carry distinct data streams, thereby enabling distinct receivers to capture
their intended signal with low interference, aided by holographic
meta-surfaces. Moreover, a prototype has been performed successfully to
demonstrate two-pair multi-node communication scenario operating at 10 GHz with
QPSK/16-QAM modulation.Comment: Meta-surface, RIS, Internet-of-Things (IoT), Line-of-Sight (LoS),
Orbital Angular Momentum (OAM), holographic communications, multi-use
Novel Insights into Orbital Angular Momentum Beams: From Fundamentals, Devices to Applications
It is well-known by now that the angular momentum carried by elementary particles can be categorized as spin angular momentum (SAM) and orbital angular momentum (OAM). In the early 1900s, Poynting recognized that a particle, such as a photon, can carry SAM, which has only two possible states, i.e., clockwise and anticlockwise circular polarization states. However, only fairly recently, in 1992, Allen et al. discovered that photons with helical phase fronts can carry OAM, which has infinite orthogonal states. In the past two decades, the OAM-carrying beam, due to its unique features, has gained increasing interest from many different research communities, including physics, chemistry, and engineering. Its twisted phase front and intensity distribution have enabled a variety of applications, such as micromanipulation, laser beam machining, nonlinear matter interactions, imaging, sensing, quantum cryptography and classical communications. This book aims to explore novel insights of OAM beams. It focuses on state-of-the-art advances in fundamental theories, devices and applications, as well as future perspectives of OAM beams
Quantum information processing with space-division multiplexing optical fibres
The optical fibre is an essential tool for our communication infrastructure
since it is the main transmission channel for optical communications. The
latest major advance in optical fibre technology is spatial division
multiplexing (SDM), where new fibre designs and components establish multiple
co-existing data channels based on light propagation over distinct transverse
optical modes. Simultaneously, there have been many recent developments in the
field of quantum information processing (QIP), with novel protocols and devices
in areas such as computing, communication and metrology. Here, we review recent
works implementing QIP protocols with SDM optical fibres, and discuss new
possibilities for manipulating quantum systems based on this technology.Comment: Originally submitted version. Please see published version for
improved layout, new tables and updated references following review proces
Roadmap on structured light
Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized.Peer ReviewedPostprint (published version
Roadmap on structured light
Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized
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