Feeds

Fibre system reach doubled in university study

All you need is a little bit of maths

  • alert
  • submit to reddit

Beginner's guide to SSL certificates

Today's optical fibre systems have twice the theoretical capacity currently attributed to them, according to research from the University of Tel Aviv.

The study, published on Arxiv, is part of the widespread academic interest in studying the channel capacity of fibre optic systems. Over long distances, and particular where wavelength division multiplexing is used, fibre systems run into constraints caused by noise, and channel capacity falls as distance increases.

An accurate prediction of systems' theoretical maximum capacity is of keen practical interest to system owners and engineers, since it feeds into investment decisions such as “do we start designing a new submarine cable system, or will we be able to get more capacity out of the old fibre in five years?” As the researchers note, the world's hunger for capacity is growing so fast that “the latest capacity estimates are being rapidly approached by the rates of commercial communication systems.”

WDM is a particular problem because of a non-linear effect called cross-phase modulation, or XPM, one of the greatest sources of noise in WDM systems. As the paper puts it, nonlinear effects in the optical fibre “generates complicated distortions of the transmitted optical waveforms.”

In a perfect world, an optical signal on wavelength A would not affect the transmission on wavelength B, but in XPM, the distortion that each wavelength experiences shows up as noise on the other wavelength and eats into its capacity.

The group, comprising Ronen Dar, Mark Shtaif and Meir Feder of the University of Tel Aviv, suggests that the noise itself can be used to improve the capacity of the systems. What they've found is that the XPM shows “strong temporal correlations” that can be used to create filters to eliminate it.

By taking advantage of those temporal correlations to analyse the channel noise, they say, the peak capacity of each channel on a WDM system can be increased by 1 bit/s per Hertz, “equivalent to doubling the SNR [signal-to-noise ratio – editor] in a linear system.

“Equivalently, we showed that the length of a system can be doubled for a given transmission rate,” the paper concludes.

Putting the paper's extensive mathematics into practise would, The Register assumes, mean designing end-systems that take advantage of this effect. ®

Remote control for virtualized desktops

More from The Register

next story
Mighty Blighty broadbanders beg: Let us lay cable in BT's, er, ducts
Complain to Ofcom that telco has 'effective monopoly'
Download alert: Nearly ALL top 100 Android, iOS paid apps hacked
Attack of the Clones? Yeah, but much, much scarier – report
Yahoo! blames! MONSTER! email! OUTAGE! on! CUT! CABLE! bungle!
Weekend woe for BT as telco struggles to restore service
Fujitsu CTO: We'll be 3D-printing tech execs in 15 years
Fleshy techie disses network neutrality, helmet-less motorcyclists
Soz, web devs: Google snatches its Wallet off the table
Killing off web service in 3 months... but app-happy bonkers are fine
Ofcom tackles complaint over Premier League footie TV rights
Virgin Media: UK fans pay the most for the fewest matches
FCC: Gonna need y'all to cough up $1.5bn to put broadband in schools
Kids need more fiber, says Wheeler, and you'll pay for it
prev story

Whitepapers

Designing and building an open ITOA architecture
Learn about a new IT data taxonomy defined by the four data sources of IT visibility: wire, machine, agent, and synthetic data sets.
5 critical considerations for enterprise cloud backup
Key considerations when evaluating cloud backup solutions to ensure adequate protection security and availability of enterprise data.
Getting started with customer-focused identity management
Learn why identity is a fundamental requirement to digital growth, and how without it there is no way to identify and engage customers in a meaningful way.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Protecting against web application threats using SSL
SSL encryption can protect server‐to‐server communications, client devices, cloud resources, and other endpoints in order to help prevent the risk of data loss and losing customer trust.