Researchers demonstrate the ability to multiplex and transfer data between twisted beams of light with different amounts of orbital angular momentum — a development that provides new opportunities for increasing the data capacity of free-space optical communications links.

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Terabit free-space data transmission employing orbital angular momentum multiplexing

A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Supercontinuum generation in photonic crystal fiber

This Review summarizes the simultaneous transmission of several independent spatial channels of light along optical fibres to expand the data-carrying capacity of optical communications. Recent results achieved in both multicore and multimode optical fibres are documented.

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Space-division multiplexing in optical fibres

Metamaterials, artificial electromagnetic media that are structured on the subwavelength scale, were initially suggested for the negative-index 'superlens'. Later metamaterials became a paradigm for engineering electromagnetic space and controlling propagation of waves: the field of transformation optics was born. The research agenda is now shifting towards achieving tunable, switchable, nonlinear and sensing functionalities. It is therefore timely to discuss the emerging field of metadevices where we define the devices as having unique and useful functionalities that are realized by structuring of functional matter on the subwavelength scale. In this Review we summarize research on photonic, terahertz and microwave electromagnetic metamaterials and metadevices with functionalities attained through the exploitation of phase-change media, semiconductors, graphene, carbon nanotubes and liquid crystals. The Review also encompasses microelectromechanical metadevices, metadevices engaging the nonlinear and quantum response of superconductors, electrostatic and optomechanical forces and nonlinear metadevices incorporating lumped nonlinear components.

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From metamaterials to metadevices.

The rise in output power from rare-earth-doped fiber sources over the past decade, via the use of cladding-pumped fiber architectures, has been dramatic, leading to a range of fiber-based devices with outstanding performance in terms of output power, beam quality, overall efficiency, and flexibility with regard to operating wavelength and radiation format. This success in the high-power arena is largely due to the fiber’s geometry, which provides considerable resilience to the effects of heat generation in the core, and facilitates efficient conversion from relatively low-brightness diode pump radiation to high-brightness laser output. In this paper we review the current state of the art in terms of continuous-wave and pulsed performance of ytterbium-doped fiber lasers, the current fiber gain medium of choice, and by far the most developed in terms of high-power performance. We then review the current status and challenges of extending the technology to other rare-earth dopants and associated wavelengths of operation. Throughout we identify the key factors currently limiting fiber laser performance in different operating regimes—in particular thermal management, optical nonlinearity, and damage. Finally, we speculate as to the likely developments in pump laser technology, fiber design and fabrication, architectural approaches, and functionality that lie ahead in the coming decade and the implications they have on fiber laser performance and industrial/scientific adoption.

High power fiber lasers: current status and future perspectives [Invited]

Bragg gratings in optical fibre waveguides have now been around for nearly 25 years and they were soon after being realised identified as one of the most significant fibre-optic inventions with potentials in a wide variety of areas among telecommunications equivalent to that of the erbium doped fibre amplifier. Following their creation a plurality of infibre functions were thought possible with low or no insertion-loss. Although fabrication and control of vital grating parameters was limited in the early stages of their life, initially a number of filtering functions were identified for obvious demonstrations. It soon became apparent though that not just standard filtering manipulation was possible. Identifying the true potential of the devices has let to considerable effort being concentrated on their full exploitation implying building an infrastructure supported by theoretical design [2] and manufacturing techniques [3,4] around them. These techniques combined have let to a scenario where currently it is the imagination more than the actual design and manufacturing capabilities that imposes a limitation to what is being demonstrated. We will in this presentation discuss and highlight some of the most recent advances in Bragg grating devices and applications in advanced components. In particular we will show examples of the latest in Bragg gratings for dispersion-control, short pulse manipulation and advanced filtering applications and speculate into what the future holds for these unique devices.

Advanced fibre Bragg gratings and where they are going

Wavelength conversion of 20 Gb/s quadrature phase shift keying (QPSK) signals is demonstrated in a tapered silicon core fiber extending across the S-, C- and L-bands. The results indicate the platform's suitability for use in broadband all-optical communication systems.

Tapered Submicron Silicon Core Fiber for Broadband Wavelength Conversion

Multi-element Fibers (MEFs) are presented as an alternative spatial division multiplexing (SDM) technology which can address some of the drawbacks that current implementations exhibit. The benefits obtained from this fiber geometry show that MEF can be a cost-effective solution for SDM implementation in commercial optical networks.

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Space Division Multiplexing Using Multi-Element Fibers

We demonstrate selective transmission and absorption of 1-ps pulses, pulse shaping and 1-ps dark pulse generation in a fiber-optic device based on a plasmonic metamaterial, providing an example of all-optical signal processing with THz bandwidth.

/pdf/a-fiberized-metamaterial-device-for-ultrafast-control-of-51uykvu3i6.pdf

A Fiberized Metamaterial Device for Ultrafast Control of Coherent Optical Signals

We review recent results on the regeneration of phase encoded (BPSK, QPSK) signals and discuss paths towards regeneration of amplitude/phase encoded (QAM) signals. Regeneration based on phase sensitive amplification will be discussed in detail.

https://eprints.soton.ac.uk/362266/1/6300.pdf

Periklis Petropoulos

Papers

Advanced fibre Bragg gratings and where they are going

Tapered Submicron Silicon Core Fiber for Broadband Wavelength Conversion

Space Division Multiplexing Using Multi-Element Fibers

A Fiberized Metamaterial Device for Ultrafast Control of Coherent Optical Signals

Signal regeneration techniques for advanced modulation formats