The electronics revolution keeps
rolling along. This trick will make the
ultimate holodeck much closer. A room
covered with interactive adjoining screens is completely plausible even today
and screen data density levels up to the task of realistic holographic imaging
is been rapidly approached. This
wireless communication trick will be perfect even at short range. Thus all the screens
could be operated independently and simultaneously from a master.
I think we are seriously about
ten years out now. That gives us just
enough time to upgrade the historical film stock to some form of three
dimensional presentation protocols.
The future work space can be a
holodeck cockpit in which the entirety of one’s perceptive space can be
anything you want, even the bridge of the Starship Enterprise. I no longer think that we have any issues
setting it up and actually making it all happen even somewhat crudely today.
Adding a Twist dimension to communication for 2.5 terabits per second
now and hundreds of times more later
JUNE 25, 2012
Extreme Tech - American and Israeli researchers have used twisted,
vortex beams to transmit data at 2.5 terabits per second. This twist
encoding technique is likely to be used in the next few years to vastly
increase the throughput of both wireless and fiber-optic networks.
These twisted signals use orbital angular momentum (OAM) to cram much
more data into a single stream. In current state-of-the-art transmission
protocols (WiFi, LTE, COFDM), we only modulate the spin angular momentum (SAM)
of radio waves, not the OAM. If you picture the Earth, SAM is our planet
spinning on its axis, while OAM is our movement around the Sun. Basically, the
breakthrough here is that researchers have created a wireless network protocol
that uses both OAM and SAM.
According to Thide, OAM should allow us to twist together an “infinite number” of conventional transmission protocols without using any more spectrum. In theory, we should be able to take 10 (or 100 or 1000 or…) WiFi or LTE signals and twist them into a single beam, increasing throughput by 10 (or 100 or 1000 or…) times.
The next task for Willner’s team will be to increase the OAM network’s paltry one-meter transmission distance to something a little more usable. “For situations that require high capacity… over relatively short distances of less than 1km, this approach could be appealing. Of course, there are also opportunities for long-distance satellite-to-satellite communications in space, where turbulence is not an issue,” Willner tells the BBC. In reality, the main limiting factor is that we simply don’t have the hardware or software to manipulate OAM. The future of wireless networking is very bright indeed.
According to Thide, OAM should allow us to twist together an “infinite number” of conventional transmission protocols without using any more spectrum. In theory, we should be able to take 10 (or 100 or 1000 or…) WiFi or LTE signals and twist them into a single beam, increasing throughput by 10 (or 100 or 1000 or…) times.
The next task for Willner’s team will be to increase the OAM network’s paltry one-meter transmission distance to something a little more usable. “For situations that require high capacity… over relatively short distances of less than 1km, this approach could be appealing. Of course, there are also opportunities for long-distance satellite-to-satellite communications in space, where turbulence is not an issue,” Willner tells the BBC. In reality, the main limiting factor is that we simply don’t have the hardware or software to manipulate OAM. The future of wireless networking is very bright indeed.
Concept and Principle - a, Generation of an information-carrying OAM beam with
a helical phase front. b, Recovery of an information-carrying beam with a
planar phase front. c, Multiplexing/demultiplexing of information-carrying OAM
beams together with polarizatio
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.
Experimental results of the multiplexing/demultiplexing of four
pol-muxed 10.7X4 Gbit s-1 16-QAM-carrying OAM beams (OAM+4, OAM+8, OAM-8,
OAM+16). a1-a4, Four computer-generated spiral phase masks with charges of -4,
+8, -8 and -16 loaded into SLM4, SLM3, SLM2 and SLM1.
Implementation details of the experimental setup. A,C,D,E, multiplexing/demultiplexing of information-carrying OAM beams; B,C,F, data exchange between OAM beams. (D)QPSK, (differential) quadrature phase-shift keying; 16-QAM, quadrature amplitude modulation; PC, polarization controller; EDFA, erbium-doped fibre amplifier; BPF, band-pass filter; DGD, differential group delay; Pol., polarizer; TDL, tunable delay line; AM, amplitude modulator; OC, optical coupler; Col., collimator; HWP, half-wave plate; SLM1-6, spatial light modulator; BS1-3, non-polarizing beamsplitter; BS4, BS5, polarizing beamsplitter; M1-M4, mirror; PM, power metre; EAM, electroabsorption modulator; Att, attenuator; DLI, delay-line interferometre; Rx, receiver; LO, local oscillator; ADC, analog-to-digital converter; DSP, digital signal processing.
Experimental (b) and theoretical results (c1-c5,d1-d3,e1-e4,f1-f3,g1-g3) of the multiplexing/demultiplexing of four OAM beams (OAM-8, OAM+10, OAM+12, OAM-14).
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