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40Gb TO 100Gb: meeting exponential bandwidth needs


Preventing a worldwide bandwidth crisis hangs by a thread – a fiber-optic thread thinner than a human hair yet filled with untapped potential, writes Nortel country manager Magda Engelbrecht.

And, that potential within each tiny fiber-optic thread is powerful enough to keep vast amounts of information like YouTube videos flowing at the speed of light, when new network technologies meet the challenge of doing what many said couldn't be done.
Today's 10 gigabit per second (10G) optical networks form the high-speed, backbone core for communications, spanning nations and linking continents into a seamless global village. But these networks – filled with thousands of tiny, fiber-optic threads – are quickly evolving from the 'fiber glut' of unused capacity built out during the late 1990s boom to possible 'fiber crisis,' as the insatiable global appetite for bandwidth threatens to choke optical networks to a crawl.
It is estimated that YouTube alone consumes as much bandwidth today as the entire Internet used in 2000, even before music downloads, online gaming and business uses like VoIP or videoconferencing are factored in. And, the trend to Hyperconnectivity, where everything that can be connected, is already fueling huge increases in devices and applications accessing networks. Nortel estimates that by 2010 there will 10 devices connected to the network for every person using them, resulting in five billion connection points.
"Growing traffic patterns with the infusion of video are causing bandwidth constraints in carrier networks worldwide. This trend has the potential to starve new, innovative Internet-based websites, applications, and services of the bandwidth they need, as well as create problems for users accessing real-time content," says Michael Howard, principal analyst at Infonetics Research.
With this unprecedented demand for bandwidth, it's little wonder carriers and service providers are starting to fuss over how to squeeze more gigabit capacity into their networks' fiber-optic threads. They're looking for affordable new technologies to boost current 10G networks to 40G, and then 100G capabilities that will keep Internet junkies satisfied with the real-time speed of their connections without jacking up subscriber fees to pay for expensive network upgrades.
But we're approaching the point where optical networks could hit a wall of limitations, governed by the basic laws of physics. And, if the quality of realtime communications is affected as a result, it will get everyone's attention – fast.
All information like videos, VoIP and multimedia services is converted into tiny packets of light to be transmitted across the fiber-optic threads of optical networks. In the same way a highway can only carry so many cars traveling at high speeds before everyone gets backed up in a huge traffic jam, networks also have limits to how much high-bandwidth information can be transmitted. As networks reach these limits for the gigabit capacity critical to quality, real-time communications, streaming video can freeze or a VoIP conversation gets garbled and starts to break up.
Overcoming those limitations of physics in simple, affordable ways that many thought weren't possible just a few years ago.  Nortel has developed the industry's first optical technology that can deliver both 40G and 100G network capacity, enabling four times the network throughput immediately, while providing the foundation to simply and affordably increase capacity tenfold as required. For example, where a current network speed of 10G can support the bandwidth of 1 000 HDTV channels simultaneously, that increases to 4 000 channels with 40G and 10 000 for 100G, speeding up downloads from hours to minutes.
Nortel's new 40G to 100G technology achieves these breakthrough milestones through simple 'plug and play' technology components added to existing 10G networks. The components allow carriers to get much more bandwidth from fiber already in use, without the need for new, expensive equipment to keep information powered up over thousands of kilometres.
"One misconception about the unused capacity from the late 1990s is that it could just be increased to handle the surge in bandwidth demand.  But not all fiber is created equal. While the quality of some fiber is fine at 2.5G or even 10G, it can distort communications signals at 40G and more. If, for example, the fiber is not perfectly round or the quality of glass isn't consistent, then the effectiveness of transmitting light signals can be hampered.
Also, when the increased amounts of information, or bandwidth, required to reach 40G is packed into the same fiber space as 10G, the different spectrums of light used to transmit it can overlap, mix together or bits lag behind. In the fiber-optic realm, where lasers are pulsing information out at billions of times per second, even one picosecond delay-one millionth of one millionth of a second – can distort up the signal. The farther the light signal travels without passing through equipment that cleans it up and puts it back together, with a boost of speed for the next leg of its journey, the more distorted it becomes.
Rather than trying to make information go four times faster to reach 40G which makes fiber quality issues even worse, Nortel has developed an approach for packing four times the amount of information into the same 10G transmission speeds that already are working well in today's networks. For example, instead of 10 cars speeding together as one unit through one lane of highway, now 40 cars occupy the same space. And, similar juggling within light frequencies will get a 40G network to 100G.
But getting four times the information to its destination also means the equipment that cleans up the signals and keeps it powered over thousands of kilometers has to be super-fast and efficient to handle four times the amount of processing. With a patent pending, Nortel invented a chip for electronic dispersion compensation (eDCO) that can figure out the errors in signals that developed over 2 000 kms, fix them and send a clean signal on its way.
In 2005, when Nortel first announced eDCO – which is the approach Nortel is taking for 10G, 40G and 100G, people said it couldn't be done, particularly using electronic techniques within less than perfect fiber.  Researchers even published critical papers saying why our chip wouldn't work.  There are now 6 000 of them in use with customers today and they are functioning as planned.
Operators are embracing Nortel's new 40G technology, creating momentum in the market with numerous network trials underway globally. Verizon Business recently purchased ultra long haul (ULH) optical equipment, which supports emerging 40G services, to enable high-bandwidth applications and deliver increased network capacity across Europe.
TDC, Denmark's leading provider of communications solutions, is deploying a new 40G-ready optical solution initially to carry TDC European network traffic across the United Kingdom, the Netherlands and Germany. Neos, a leading service provider in the UK, is deploying a 40G solution to provide bandwidth-on-demand to its customers.