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Optical/IP

OFC/NFOEC 2011: Bandwidth Goes Flexible, Too

LOS ANGELES -- OFC/NFOEC 2011 -- There's already been talk that 1Tbit/s transmission will need a flexible wavelength grid. Now, vendors and some carriers are talking about letting the speed of a connection change as well.

You could call it software-defined optics, because the concept is the same as the software-defined radio that's pervasive in wireless communications. More formally, it tends to go by the name adaptive modulation and coding.

Whatever you call it, the flexible bandwidth idea got some buzz at OFC/NFOEC. It's an old idea, even in optical circles, but it's getting some consideration as a means of extending the reach of high-speed transmission. It also helped that the topic was discussed at a Sunday workshop before the conference.

The idea would be to let carriers change the modulation scheme or the strength of Forward Error Correction (FEC) on a particular interface. This could buy them extended reach where needed, or let them ratchet up some speed on shorter routers.

"That's what we believe is the next step," says Christoph Glingener, CTO of ADVA Optical Networking . "I think it's well received, but I also think it's four or five years out."

That's not too early for vendors to insert the idea into the conversation, of course. In addition to ADVA, Infinera Corp. (Nasdaq: INFN) says it's got that technology in its 500Gbit/s and 1Tbit/s photonic integrated circuits (PICs).

It's a sign of coming flexibility in networks. Already, carriers and vendors are considering the possibility of loosening up the ITU grid for wavelengths, because there's a suspicion that 400Gbit/s or 1Tbit/s channels might need wider bandwidth than the grid allows. (See ROADMs Get Ready to Go Off-Grid and OFC/NFOEC: For ROADMs, Less Is More.)

(As a side note, that gridless aspect for reconfigurable optical add/drop multiplexers (ROADMs) might get standardized soon. Simon Poole, director of new business ventures at Finisar Corp. (Nasdaq: FNSR), says his company is proposing an ITU-T G.694.1 update that defines varying grid widths in 12.5GHz increments.)

One question around adaptive modulation and coding is whether the big carriers want to be that adaptive. With a reputation for wanting rigid standards and performance metrics, some large telcos don't seem to have the personality to let speeds fluctuate on the network.

"At first, maybe you will only do two bit rates, maybe in two years," with greater flexibility coming in maybe five years, Glingener says. "But in the advanced research community, it's known. People are looking at it."

— Craig Matsumoto, West Coast Editor, Light Reading

Pete Baldwin 12/5/2012 | 5:10:36 PM
re: OFC/NFOEC 2011: Bandwidth Goes Flexible, Too

Regarding big U.S. carriers, here's my understanding: AT&T likes to launch speeds in pairs -- it'll run 10 and 40Gbit/s on its fibers for a time, then upgrade to 40 and 100Gbit/s.  But only TWO at a time.

Meanwhile, I've heard second-hand (but haven't had time to confirm) that Verizon already likes the idea of variable speeds.

This would certainly fit the two company's reputations.

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