Tag Archives: physical layer

Scientists Have Broken One of the Biggest Limits in Fibre Optic Networks

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Essentially what the UC San Diego researchers did was to develop a system (frequency comb) that acts a bit like a concert conductor, which is the person responsible for tuning multiple instruments in an orchestra to the same pitch at the beginning of a concert.

The engineers then used this comb to synchronize the frequency variations of the different streams of optical information (optical carriers), which can compensate in advance for the crosstalk interference (this will be familiar to those who have been reading about FTTC / VDSL2 Vectoring technology on copper cables) that can occur between multiple communication channels within the fibre optic cable. The frequency comb also ensures that the crosstalk interference is reversible.

Source: Scientists Have Broken One of the Biggest Limits in Fibre Optic Networks – ISPreview UK

World Record as Alcatel-Lucent Push 10Gbps Broadband Down Copper Lines

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Bell Labs achieved 1Gbps symmetrical over just 70 meters on a single copper pair and 10Gbps was achieved over a distance of 30 meters by using two pairs of lines bonding. Both tests used standard copper cable provided by a European operator. The speeds are impressive but the distance is clearly more problematic, which might mean more of a choir for operators as they’d need to bring the accompanying fibre optic cable even closer to your doorstep at this range you could almost call it FTTB.

via World Record as Alcatel-Lucent Push 10Gbps Broadband Down Copper Lines – ISPreview UK.

The question for some operators will be whether or not it’s even worth following the G.fast to XG-FAST path, as opposed to simply putting fibre optic cable in the ground and having less to worry about in the future.

Closing the gap to improve the capacity of existing fiber optic networks

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The research team, which included Professor Arthur Lowery and Dr Liang Du of the Monash Department of Electrical and Computer Systems Engineering and Jochen Schroeder, Joel Carpenter and Ben Eggleton from the University of Sydney, managed to transmit a signal of 10 terabits per second (Tb/s) more than 850 km (528 miles) using the new technology.

via Closing the gap to improve the capacity of existing fiber optic networks.

Docsis 3.1 Rides the Wireless Wave

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OFDM will provide Docsis with a new order of bandwidth efficiency, but it also offers some sound business reasons for cable to adopt it. OFDM, already used for Wi-Fi and Long Term Evolution (LTE), could lead to better economies of scale and get more vendors interested in the cable market, explained Daniel Howard, the SVP of engineer and CTO at Society of Cable Telecommunications Engineers (SCTE), during a webcast earlier this month on the topic (SCTE is tasked with helping the cable industry get trained up for Docsis 3.1). (See Setting the Stage for Docsis 3.1.)

via Light Reading – Docsis 3.1 Rides the Wireless Wave.

Lots of interesting info on OFDM in this article.  I find it amazing how creative people get in squeezing not just more bandwidth, but orders of magnitude more bandwidth, using the same physical outside plant infrastructure.

Quantum cryptography conquers noise problem

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Physicists have attempted to solve the problem by sending photons through a shared fibre along a ‘quantum channel’ at one characteristic wavelength. The trouble is that the fibre scatters light from the normal data traffic into that wavelength, polluting the quantum channel with stray photons. Andrew Shields, a physicist at the Toshiba Cambridge Research Laboratory, UK, and his colleagues have now developed a detector that picks out photons from this channel only if they strike it at a precise instant, calculated on the basis of when the encoded photons were sent. The team publishes its results in Physics Review X.

via Quantum cryptography conquers noise problem : Nature News & Comment.

Still, 90 kilometres is a “world record that is a big step forward in demonstrating the applicability of quantum cryptography in real-world telecommunications infrastructures”, says Vicente Martín, a physicist at the Technical University of Madrid.

Docsis 3.1 Targets 10-Gig Downstream

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ORLANDO — SCTE Cable-Tec Expo — The Docsis 3.1 platform will support capacities of at least 10Gbit/s downstream and 1Gbit/s upstream, a move that will certainly prolong the industry’s need to deploy fiber all the way to the home.

via Light Reading Cable – Cable – Docsis 3.1 Targets 10-Gig Downstream – Telecom News Analysis.

To hit its capacity targets, the cable industry wants to increase its spectral efficiency by about 50 percent. As expected, the new specs will do away with 6MHz- and 8MHz-wide channel spacing and instead use smaller (20KHz-to-50KHz-wide) orthogonal frequency division multiplexing (OFDM) subcarriers; these can be bonded inside a block spectrum that could end up being about 200MHz wide. (See Docsis 3.1 Will Change Cable’s Data Channels.)

The definition of ofdm from wiki.

Orthogonal frequency-division multiplexing (OFDM) is a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for widebanddigital communication, whether wireless or over copper wires, used in applications such as digital television and audio broadcasting, DSLbroadband internet access, wireless networks, and 4G mobile communications.

And the primary advantage using ofdm is:

The primary advantage of OFDM over single-carrier schemes is its ability to cope with severe channel conditions (for example, attenuation of high frequencies in a long copper wire, narrowband interference and frequency-selective fading due to multipath) without complex equalization filters.  Channel equalization is simplified because OFDM may be viewed as using many slowly modulated narrowband signals rather than one rapidly modulated wideband signal.

NASA to Demonstrate Communications Via Laser Beam

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It currently takes 90 minutes to transmit high-resolution images from Mars, but NASA would like to dramatically reduce that time to just minutes. A new optical communications system that NASA plans to demonstrate in 2016 will lead the way and even allow the streaming of high-definition video from distances beyond the Moon.

via NASA – NASA to Demonstrate Communications Via Laser Beam.

The LCRD is the next step in that direction, Israel said, likening the emerging capability to land-based fiber-optic systems, such as Verizon’s FiOS network. “In a sense, we’re moving FiOS to space.”

Alcatel-Lucent Enhances VDSL2 Vectoring

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Vectoring, the market term for the ITU’s G.993.5 standard (also known as G.Vector), is a noise cancellation technology that reduces the interference between bundled copper lines and boosts the speed and reach of VDSL2 broadband connections. It is also known as DSM (Dynamic Spectrum Management) Level 3.

via Light Reading Europe – IP & Convergence – Alcatel-Lucent Enhances VDSL2 Vectoring – Telecom News Analysis.

If AlcaLu can deliver effective vectoring capabilities using installed CPE, then that’s only going to expand the market potential for its system, especially as more operators look for ways to extend the useful life of their copper plant before taking the plunge into fiber-to-the-home (FTTH).

Ethernet over Copper

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ADTRAN’s Ethernet over Copper (EoCu) products enable service providers to extend packet-based business-class services beyond the reach of their fiber networks by leveraging the existing investment of copper-based TDM business services assets. This means leveraging the full advantages of TDM, the most understood, successful, and ubiquitous business service infrastructure. Due to budget restrictions and time to market requirements, deploying fiber to address nascent or disperse service demand is not feasible. This leaves a large percentage of businesses to rely on copper business access.

via Ethernet over Copper | EoCu Products | TDM Business Services from ADTRAN.