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

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

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 11 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 16 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

http://science.sciencemag.org/content/sci/340/6140/1545.full.pdf

Terabit-Scale Orbital Angular Momentum Mode Division Multiplexing in Fibers

We report simultaneous transmission of six spatial and polarization modes, each carrying 40 Gb/s quadrature-phase-shift-keyed channels over 96 km of a low-differential group delay few-mode fiber. The channels are successfully recovered by offline DSP based on coherent detection and multiple-input multiple-output processing. A penalty of ;28 dB.

Mode-Division Multiplexing Over 96 km of Few-Mode Fiber Using Coherent 6 $\,\times\,$ 6 MIMO Processing

Fiber-optic communication systems form the high-capacity transport infrastructure that enables global broadband data services and advanced Internet applications. The desire for higher per-fiber transport capacities and, at the same time, the drive for lower costs per end-to-end transmitted information bit has led to optically routed networks with high spectral efficiencies. Among other enabling technologies, advanced optical modulation formats have become key to the design of modern wavelength division multiplexed (WDM) fiber systems. In this paper, we review optical modulation formats in the broader context of optically routed WDM networks. We discuss the generation and detection of multigigabit/s intensity- and phase-modulated formats, and highlight their resilience to key impairments found in optical networking, such as optical amplifier noise, multipath interference, chromatic dispersion, polarization-mode dispersion, WDM crosstalk, concatenated optical filtering, and fiber nonlinearity

Advanced Optical Modulation Formats

Forty 42.7-Gb/s, 100-GHz-spaced WDM channels were transmitted over 6000 km of Ultra-Wave/spl trade/ fiber using 100-km dispersion-managed fiber spans. This is the first transoceanic length DWDM demonstration at 40 Gb/s using terrestrial amplifier span lengths.

Transmission of 1.6 Tb/s (40/spl times/42.7 Gb/s) over transoceanic distance with terrestrial 100-km amplifier spans

The design of few-mode fibers will be discussed from the point of view of key attributes and fundamental limitations We will consider the maximum number of modes that might be supported in a practical fiber

Few-mode fibers for mode-division multiplexing

We demonstrated 70nm seamless band transmission of 173×128Gb/s QPSK signals over 40×100km of TeraWave™ fiber. The complementary Raman/EDFAs and wide-band single-stage discrete Raman amplifiers were used to achieve this 17.3Tb/s capacity ultra-wide single-band transmission.

70 nm seamless band transmission of 17.3 Tb/s over 40×100km of fiber using complementary Raman/EDFA

We experimentally demonstrated 70nm seamless band transmission of 173×256Gb/s PM-16QAM signals over 2400km of TeraWave™ fiber. The complementary Raman/EDFAs were used to achieve the 34.6Tb/s capacity wide single-band transmission with terrestrial fiber span length.

34.6 Tb/s (173×256Gb/s) single-band transmission over 2400km fiber using complementary Raman/EDFA

We transmitted 5 wavelength channels and 6 spatial-and polarization modes over a 184 km long hybrid span few-mode fiber span. Low-loss 3-spot mode couplers are used in combination with backward pumped distributed Raman amplification. The 40-Gbit/s QPSK signals with an aggregate line-rate of 1.2 Tbit/s were recovered by coherent multiple-input-multiple-output off-line digital signal processing.

D. W. Peckham

Papers

Transmission of 1.6 Tb/s (40/spl times/42.7 Gb/s) over transoceanic distance with terrestrial 100-km amplifier spans

Few-mode fibers for mode-division multiplexing

70 nm seamless band transmission of 17.3 Tb/s over 40×100km of fiber using complementary Raman/EDFA

34.6 Tb/s (173×256Gb/s) single-band transmission over 2400km fiber using complementary Raman/EDFA

Mode-multiplexed transmission over a 184-km DGD-compensated few-mode fiber span