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glass fiber @ 0.997 c


Information superhighway approaches light speed

18:00 24 March 2013 by Jacob Aron Nothing moves faster than light in a
vacuum, but large volumes of data can now travel at 99.7 per cent of this
ultimate speed limit.

In glass optical fibres, light travels 31 per cent slower than in a vacuum.
Hollowing them out so that most of the light travels through air speeds
things up. But these hollow fibres are a poor replacement as light scatters
at the glass-air interface, limiting the number of wavelengths, and therefore
the volume of data, transmitted at once.

Now Francesco Poletti and colleagues at the University of Southampton, UK,
have made fibres with an ultra-thin glass rim, enabling a much wider band of
wavelengths to travel at high speed at once. The team's record is a 73.7
terabit per second transmission over 310?metres, a 15,000-fold increase over
ordinary hollow fibres.

"Previous fibres either have higher bandwidth but high loss, or lower loss
but narrower bandwidth," says Poletti. "We've achieved both in the same

Journal reference: Nature Photonics, DOI: 10.1038/nphoton.2013.45


Towards high-capacity fibre-optic communications at the speed of light in

F. Poletti,	 N. V. Wheeler,	 M. N. Petrovich,	 N. Baddela,	 E.
Numkam Fokoua,	 J. R. Hayes,	 D. R. Gray,	 Z. Li,	 R. Slav?k	 & D.
J. Richardson Nature Photonics (2013) doi:10.1038/nphoton.2013.45

Received 13 September 2012 Accepted 08 February 2013 Published online 24
March 2013


Wide-bandwidth signal transmission with low latency is emerging as a key
requirement in a number of applications, including the development of future
exaflop-scale supercomputers, financial algorithmic trading and cloud
computing1, 2, 3. Optical fibres provide unsurpassed transmission bandwidth,
but light propagates 31% slower in a silica glass fibre than in vacuum, thus
compromising latency. Air guidance in hollow-core fibres can reduce fibre
latency very significantly. However, state-of-the-art technology cannot
achieve the combined values of loss, bandwidth and mode-coupling
characteristics required for high-capacity data transmission. Here, we report
a fundamentally improved hollow-core photonic-bandgap fibre that provides a
record combination of low loss (3.5 dB km?1) and wide bandwidth (160 nm), and
use it to transmit 37 ? 40 Gbit s?1 channels at a 1.54 ?s km?1 faster speed
than in a conventional fibre. This represents the first experimental
demonstration of fibre-based wavelength division multiplexed data
transmission at close to (99.7%) the speed of light in vacuum.