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Optical/IP

Nortel Rolls On With 40-Gig

Nortel Networks Ltd. has scored another pair of 40-Gbit/s wins, including a big-name signing with BCE Inc. (Bell Canada) (NYSE/Toronto: BCE).

That brings its 40-Gbit/s scorecard to 21 contracts, though most of them are with smaller carriers such as Alaska Communications Systems Inc. (ACS) , which was also named today as a new customer.

It's a streak Nortel has ridden since November 2007, when it announced that its Optical Multiservice Edge (OME) 6500 got picked for the Verizon Enterprise Solutions pan-European buildout. The technology in question started shipping in April. (See Nortel Takes 40-Gig to Verizon.)

The key has been Nortel's ability to run 40-Gbit/s signals on 10-Gbit/s infrastructure, says Infonetics Research Inc. analyst Michael Howard.

"What happens with most of the 40-Gbit/s modulation schemes is that you run at a 40-Gbit/s rate or a 20-Gbit/s rate," Howard says. On most fiber, those kinds of data rates introduce chromatic dispersion or polarization mode dispersion -- in other words, the signal starts getting gunked up, and the network must be re-engineered to compensate.

Nortel's technology runs at a 10-Gbit/s rate, using dual polarization quadrature phase shift keying (DPQPSK) to send 40-Gbit/s worth of data. That means no re-engineering; to other optical equipment, Nortel looks as if it's sending a normal 10 Gbit/s signal. (See Nortel Trots Out 40Gig.)

That lets Nortel bring the OME 6500's 40-Gbit/s capability into networks populated by other vendors' equipment -- and that's been key to many of the company's wins so far, says Philippe Morin, Nortel's president of metro Ethernet networking.

Other competitors such as Nokia Networks , which Howard says "is certainly, as of last year, the leader in 40 Gbit/s," haven't yet applied DPQPSK to 40-Gbit/s systems. Most vendors will end up working with the modulation scheme, though, if only because it's looking like the choice for 100-Gbit/s optical networking.

For now, much of Nortel's competition at 40-Gbit/s is coming from startups. OpVista Inc. is similarly claiming to produce 40-Gbit/s data rates using 10-Gbit/s wavelengths, but its CX8 system hasn't gotten up to production volumes yet. (See OpVista Runs With DMC for 40-Gig.)

Mintera Corp. and StrataLight Communications get mentioned more frequently, especially with the former having partnered with JDSU (Nasdaq: JDSU; Toronto: JDU) and the latter being acquired by Opnext Inc. (Nasdaq: OPXT). (See Mintera Adds Cash, Partner, Mintera Challenges StrataLight in 40G Fight, and Opnext Steps Up With StrataLight.)

CoreOptics Inc. also offers 40-Gbit/s transponder subsystems.

While Nortel now has Bell Canada, Verizon Business, and Virgin Media Inc. (Nasdaq: VMED) as customers, most of its announced 40-Gbit/s wins have been with smaller companies like ACS. (See Virgin Trials 40-Gig, Rascom Uses Nortel Optical, and Nortel 40G Goes South.)

Morin credits that to the smaller scale of smaller carriers -- it's easier for them to do things like migrate to a faster speed grade.

Some big carriers have gotten to 40 Gbit/s: AT&T Inc. (NYSE: T), for instance, began running an OC768 backbone in 2007. (See AT&T Readies 40-Gig Backbone.) Nortel's hope is that more of them are readying plans to migrate up. "We're getting into the next wave, the bigger-scale type of network," Morin says.

— Craig Matsumoto, West Coast Editor, Light Reading

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digits 12/5/2012 | 3:33:06 PM
re: Nortel Rolls On With 40-Gig Will DPQPSK become the de facto choice for 40G and 100G deployments?
nodak 12/5/2012 | 3:33:04 PM
re: Nortel Rolls On With 40-Gig If Verizon and ATT are running trials for 100G, how much 40G will they want to buy now?

NoCopper 12/5/2012 | 3:33:03 PM
re: Nortel Rolls On With 40-Gig Boozon, I would be very interested to know why PM-QPSK has no none linear effect issues at 100G while you claim that there are issues at 40G? This does not make any sense to me.

In fact there might be issues with high launch power into DCSMs with any phase modulated technology, regardless whether its 40G or 100G. You say that PM-QPSK will be the industry choice for 100G and I totally agree. But that's exactly why "100G ready" optical line systems either avoid DSCMs at all or you make sure that the launch power into a DSCM does not exceed about 0dBm.

boozon 12/5/2012 | 3:33:03 PM
re: Nortel Rolls On With 40-Gig Have you read the OFC OTuM5 paper by ALU that shows the high nonlinear cross talk that 40G PM-QPSK (or DPQPSK) suffers from neighboring 10G NRZ channels in a system with in-line DCMs?
Unless the carriers get rid of all their in-line DCMs it's difficult to see how this modulation format will become the de facto choice at 40G.
As a matter of fact, a few thousands of 40G line cards deployed to date on existing infrastructure use PSBT (aka ODB) and DPSK modulation schemes, whereas you can find only a few tens (at most) of PM-QPSK cards in the field.
Maybe there's the answer to your question...

Whereas the 40G best modulation scheme is still a very debated topic it seems that everybody converges to PM-QPSK for 100G, where the non linear effects with neighboring channels are not as bad as at 40G. This is good news as large economies of scale will be achievable if all systems use the same components.

AutoDog 12/5/2012 | 3:33:02 PM
re: Nortel Rolls On With 40-Gig The DCM issue is significant... If the PM-QPSK terminal equipment can only tolerate adjacent 10G lambda in systems without DCMs, then this could significantly limit where this new gear could be deployed.

Perhaps this is a known limitation of the first Nortel PM-QPSK gear, but a truly flexible solution would be for upcoming designs their PM-QPSK systems to accommodate 10G neighbors with DCMs.

-AD
boozon 12/5/2012 | 3:33:02 PM
re: Nortel Rolls On With 40-Gig NoCopper, who said that there are no nonlinear effects at PM-QPSK 100G?
There are but they're not as bad as at 40G.
Why?
Because the 40G symbol duration matches the 10G bit period, whereas this is not the case at 100G. Therefore there is some averaging of the non linear effects at 100G whereas at 40G the NL effects experienced in every span add up.
This is the Mickey Mouse explanation, and I don't pretend that it's very rigorous.
You can find a more scientific one the several technical papers on this topic (starting from the OFC one I mentioned).

nodak 12/5/2012 | 3:32:56 PM
re: Nortel Rolls On With 40-Gig When you say DCM, are you talking about fiber based DCM, grating based DCM, or both?
alandal 12/5/2012 | 3:32:53 PM
re: Nortel Rolls On With 40-Gig Is it because that 100G will be running at 4 WDM lanes instead of a single WDM lane used by the current 40G DPQPSK implementation?
Petabit 12/5/2012 | 3:32:52 PM
re: Nortel Rolls On With 40-Gig Is this the same Lucent research team that spent the last five years publishing papers showing that electronic dispersion pre-compensation could not possibly work, when Nortel we selling working systems?

Yes there are problems with XPM when you launch at high powers into DCMs. The answer? Dial down the power, and use coherent detection to improve the SNR. Same trick that submarine systems have been using for years.

If the Nortel 40G did not work, how are they selling it to so many people?

P
^Eagle^ 12/5/2012 | 3:32:52 PM
re: Nortel Rolls On With 40-Gig nope, the 100g implementation will still use only 1 wdm lambda... same as pol-muxed DQPSK at 40G.

That is on the line side.

on the client side, it will likely be 4x25g using 4 optical wavelengths up to 10km...

sailboat
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