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Orbital Angular Momentum And Wavelength Demultiplexing Using Tunable MEMS-based Fabry-Pérot Filter Integrated With Spiral Phase Plate
Abstract
We experimentally demonstrate simultaneous orbital angular momentum (OAM) and wavelength (de)multiplexing of 10 Gbit/s data streams around 1550 nm using new on-chip micro-component tunable MEMS-based Fabry-Pérot filter integrated with a spiral phase plate. The proposed device can be useful for future high-capacity optical communications with simultaneous OAM- and wavelength-division multiplexing, especially in short-range communication scenarios and optical interconnects.
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We demonstrate an on-chip device capable of wavelength-selective generation of vortex beams, which is realized by a spiral phase plate integrated onto a microelectromechanical system (MEMS) tunable filter. This vortex MEMS filter, being capable of functioning simultaneously in both wavelength and orbital-angular-momentum (OAM) domains at the 1550 nm wavelength regime, is considered as a compact, robust, and cost-effective solution for simultaneous OAM- and wavelength-division multiplexed optical communications. The experimental OAM spectra for azimuthal orders 1, 2, and 3 show an OAM state purity > 92 % across a wavelength range of more than 30 nm.
This issue of Philosophical Transactions of the Royal Society, Part A represents a summary of the recent discussion meeting 'Communication networks beyond the capacity crunch'. The purpose of the meeting was to establish the nature of the capacity crunch, estimate the time scales associated with it and to begin to find solutions to enable continued growth in a post-crunch era. The meeting confirmed that, in addition to a capacity shortage within a single optical fibre, many other 'crunches' are foreseen in the field of communications, both societal and technical. Technical crunches identified included the nonlinear Shannon limit, wireless spectrum, distribution of 5G signals (front haul and back haul), while societal influences included net neutrality, creative content generation and distribution and latency, and finally energy and cost. The meeting concluded with the observation that these many crunches are genuine and may influence our future use of technology, but encouragingly noted that research and business practice are already moving to alleviate many of the negative consequences.
Vector modes are spatial modes that have spatially inhomogeneous states of polarization, such as, radial and azimuthal polarization. In this work, the spatially inhomogeneous states of polarization of vector modes are used to increase the transmission data rate of free-space optical communication via mode division multiplexing. A mode (de)multiplexer for vector modes based on a liquid crystal q -plate is introduced. As a proof of principle, four vector modes each carrying a 20-Gbit/s quadrature phase shift keying signal (aggregate 80 Gbit/s) on a single wavelength channel ( λ ∼ 1550 nm ) were transmitted ∼ 1 m over the lab table with < − 16.4 dB mode crosstalk. Bit error rates for all vector modes were measured at the 7% forward error correction threshold with power penalties < 3.41 dB .
Orbital angular momentum (OAM), which describes the “phase twist” (helical phase pattern) of light beams, has recently gained interest due to its potential applications in many diverse areas. Particularly promising is the use of OAM for optical communications since: (i) coaxially propagating OAM beams with different azimuthal OAM states are mutually orthogonal, (ii) inter-beam crosstalk can be minimized, and (iii) the beams can be efficiently multiplexed and demultiplexed. As a result, multiple OAM states could be used as different carriers for multiplexing and transmitting multiple data streams, thereby potentially increasing the system capacity. In this paper, we review recent progress in OAM beam generation/detection, multiplexing/demultiplexing, and its potential applications in different scenarios including free-space optical communications, fiber-optic communications, and RF communications. Technical challenges and perspectives of OAM beams are also discussed.
Harnessing the orbital angular momentum (OAM) of light is an appealing approach to developing photonic technologies for future applications in optical communications and high-dimensional quantum key distribution (QKD) systems. An outstanding challenge to the widespread uptake of the OAM resource is its efficient generation. In this work we design a new device that can directly emit an OAM-carrying light beam from a low-cost semiconductor laser. By fabricating micro-scale spiral phase plates within the aperture of a vertical-cavity surface-emitting laser (VCSEL), the linearly polarized Gaussian beam emitted by the VCSEL is converted into a beam carrying specific OAM modes and their superposition states, with high efficiency and high beam quality. This new approach to OAM generation may be particularly useful in the field of OAM-based optical and quantum communications, especially for short-reach data interconnects and QKD.
Internet data traffic capacity is rapidly reaching limits imposed by optical fiber nonlinear effects. Having almost exhausted
available degrees of freedom to orthogonally multiplex data, the possibility is now being explored of using spatial modes
of fibers to enhance data capacity. We demonstrate the viability of using the orbital angular momentum (OAM) of light to create
orthogonal, spatially distinct streams of data-transmitting channels that are multiplexed in a single fiber. Over 1.1 kilometers
of a specially designed optical fiber that minimizes mode coupling, we achieved 400-gigabits-per-second data transmission
using four angular momentum modes at a single wavelength, and 1.6 terabits per second using two OAM modes over 10 wavelengths.
These demonstrations suggest that OAM could provide an additional degree of freedom for data multiplexing in future fiber
networks.
We demonstrate a 2 Tbit / s free-space data link using two orthogonal orbital angular momentum beams each carrying 25 different wavelength-division-multiplexing channels. We measure the performance for different modulation formats, including directly detected 40 Gbit / s nonreturn-to-zero (NRZ) differential phase-shift keying, 40 Gbit / s NRZ on-off keying, and coherently-detected 10 Gbaud NRZ quadrature phase-shift keying, and achieve low bit error rates with penalties less than 5 dB.
We describe a method to estimate the capacity limit of fiber-optic communication systems (or ¿fiber channels¿) based on information theory. This paper is divided into two parts. Part 1 reviews fundamental concepts of digital communications and information theory. We treat digitization and modulation followed by information theory for channels both without and with memory. We provide explicit relationships between the commonly used signal-to-noise ratio and the optical signal-to-noise ratio. We further evaluate the performance of modulation constellations such as quadrature-amplitude modulation, combinations of amplitude-shift keying and phase-shift keying, exotic constellations, and concentric rings for an additive white Gaussian noise channel using coherent detection. Part 2 is devoted specifically to the "fiber channel.'' We review the physical phenomena present in transmission over optical fiber networks, including sources of noise, the need for optical filtering in optically-routed networks, and, most critically, the presence of fiber Kerr nonlinearity. We describe various transmission scenarios and impairment mitigation techniques, and define a fiber channel deemed to be the most relevant for communication over optically-routed networks. We proceed to evaluate a capacity limit estimate for this fiber channel using ring constellations. Several scenarios are considered, including uniform and optimized ring constellations, different fiber dispersion maps, and varying transmission distances. We further present evidences that point to the physical origin of the fiber capacity limitations and provide a comparison of recent record experiments with our capacity limit estimation.
We demonstrate the Fourier relationship between angular position and angular momentum for a light mode. In particular we measure the distribution of orbital angular momentum states of light that has passed through an aperture and verify that the orbital angular momentum distribution is given by the complex Fourier-transform of the aperture function. We use spatial light modulators, configured as diffractive optical components, to define the initial orbital angular momentum state of the beam, set the defining aperture, and measure the angular momentum spread of the resulting beam. These measurements clearly confirm the Fourier relationship between angular momentum and angular position, even at light intensities corresponding to the single photon level.
In this chapter, we provide a comprehensive review of multimode communications using OAM. The fundamentals of OAM are introduced first followed by the techniques for OAM generation, multiplexing/demultiplexing, and detection. We then present recent research efforts to free-space communication links and fiber-based transmission links using OAM multiplexing together with optical signal processing using OAM (data exchange, add/drop, multicasting, monitoring, and compensation). Future challenges of OAM communications are discussed at the end.
The recognition in the 1990s that light beams with a helical phase front
have orbital angular momentum has benefited applications ranging from
optical manipulation to quantum information processing. Recently,
attention has been directed towards the opportunities for harnessing
such beams in communications. Here, we demonstrate that four light beams
with different values of orbital angular momentum and encoded with 42.8
× 4 Gbit s-1 quadrature amplitude modulation (16-QAM)
signals can be multiplexed and demultiplexed, allowing a 1.37 Tbit
s-1 aggregated rate and 25.6 bit s-1
Hz-1 spectral efficiency when combined with polarization
multiplexing. Moreover, we show scalability in the spatial domain using
two groups of concentric rings of eight polarization-multiplexed 20
× 4 Gbit s-1 16-QAM-carrying orbital angular momentum
beams, achieving a capacity of 2.56 Tbit s-1 and spectral
efficiency of 95.7 bit s-1 Hz-1. We also report
data exchange between orbital angular momentum beams encoded with 100
Gbit s-1 differential quadrature phase-shift keying signals.
These demonstrations suggest that orbital angular momentum could be a
useful degree of freedom for increasing the capacity of free-space
communications.
The communication requirements imposed by the unabated growth in both the size and computational density of modern data centers will soon outpace the fundamental capabilities of conventional electronic interconnection networks. Optical interconnects represent a potentially disruptive technology that can simultaneously satisfy the throughput, latency, and energy demands of these next-generation systems. In this paper, we propose an end-to-end photonic networking platform for future optically-interconnected data center networks. A reconfigurable hybrid photonic network building block and a protocol-agnostic optical network interface comprise the key elements of our proposed system. A modular optical switch fabric prototyping platform is designed and implemented to support a wide variety of potential photonic technologies. We successfully demonstrate nanosecond-scale optical packet-switching at 1-Tb/s per port (40-Gb/s ×25λs) through our prototype, configured as a 4×4 switch, and confirm error-free transmission across all wavelengths. In order to flexibly allocate appropriate bandwidth for heterogeneous applications, we further implement and evaluate a novel wavelength-reconfigurable optical packet- and circuit-switch by utilizing our optical switch platform. Finally, we detail our implementation of an optical network interface card (O-NIC) designed to bridge the gap between the well-established protocol layers utilized in current networks and the physical layer of the proposed photonic networks and demonstrate its functionality by the streaming of high-definition video through the end-to-end optical network.
High-performance computing systems are of steadily growing interest to provide new levels of computational capability for an increasing range of applications. The growing use of and dependence on optical interconnects to meet these system's scaling bandwidth demands has given rise to “computercom” as a distinct market segment, alongside the traditional datacom and telecom markets. This paper discusses the trends, requirements, tradeoffs, and potential technologies for this market.
Coding for Optical Channels Ivan Djordjevic William Ryan Bane Vasic In order to adapt to the ever-increasing demands for high-speed transmission and distance-independent connectivity, today's network operators are implementing 100 Gb/s per dense wavelength division multiplexing (DWDM) channel. At those data rates, the performance of fiber-optic communication systems is degraded significantly due to intra- and inter-channel fiber nonlinearities, polarization-mode dispersion (PMD), and chromatic dispersion. In order to deal with these channel impairments, novel advanced techniques in modulation, detection, coding and signal processing are needed. This groundbreaking book represents a coherent and comprehensive introduction to the fundamentals of optical communications, digital signal processing (DSP), and coding for optical channels. This book: •Is the first to integrate the fundamentals of coding theory and DSP with the fundamentals of optical communication; •Provides detailed coverage of joint coding and modulation for optical communications; •Presents turbo equalization for joint iterative channel equalization and soft decoding on optical channels; •Provides in-depth coverage of codes on graphs, including LDPC and turbo codes, and describes their application to optical channels; •Includes coverage of both fiber-optics and free-space optical (FSO) channels; •Is the first to cover the channel capacity of fiber-optic communication systems; •Is the first to describe constrained coding for optical channels. © Springer Science+Business Media, LLC 2010. All rights reserved.
Optical vortex based Mode Division Multiplexing over graded-index multimode fiber
- J Carpenter
- B C Thomsen
- T D Wilkinson
J. Carpenter, B. C. Thomsen, T. D. Wilkinson, "Optical vortex based
Mode Division Multiplexing over graded-index multimode fiber," in
Optical Fiber Communication Conference, OSA Technical Digest
(Optical Society of America, 2013), paper OTh4G.3.
Free-space information transfer using light beams carrying orbital angular momentum
- G Gibson
- J Courtial
- M Padgett
- M Vasnetsov
- V Pasko
- S Barnett
- S Franke-Arnold
G. Gibson, J. Courtial, M. Padgett, M. Vasnetsov, V. Pasko, S. Barnett,
and S. Franke-Arnold, "Free-space information transfer using light
beams carrying orbital angular momentum," Opt. Express, vol. 12,
no. 22, pp. 5448-5456, November 2004.