New distance record for 400 Gb/s data transmission

Mar 12, 2013
This shows the measured optical spectrum of the eight 100GHz-spaced 495Gb/s WDM signals at the launch into the transmission fiber. The insets are measured constellation diagrams before and after transmission. QPSK: quadrature phase shift keying; QAM: quadrature amplitude modulation; WDM: wavelength division multiplexed. Credit: AT&T Labs

As network carriers debate the next Ethernet standard—and whether transmission speeds of 400 gigabit per second or 1 terabit per second should be the norm—engineers are working on new measures to squeeze next-generation performance out of current-generation systems.

To that end, a team from AT&T has devised a new patent pending technique enabling tuning of the modulation , which allows, for the first time, 400 Gb/s signals to be sent over today's 100 gigahertz-grid optical networks over ultra-long distances. Spectral efficiency is the information rate that can be transmitted over a given bandwidth, and measures how efficiently the available frequency spectrum is utilized.

This is about the principle of the proposed optical modulation technique having adaptable spectral efficiency. The table lists the modulation formats used in the experiment for time slots 1 and 2, as well as the modulation formats' spectral widths and the resulting range of adaptable spectral width attainable for the TDM frame from the proposed optical modulation technique. TDM: time-division-multiplexed; PM: polarization-multiplexed; QPSK: quadrature phase shift keying; QAM: quadrature amplitude modulation. Credit: AT&T Labs

The researchers, led by optical transmission system expert Xiang Zhou of AT&T Labs-Research in Middletown, N.J., will describe their work at the Optical Fiber Communication Conference and Exposition/National Fiber Optic Engineers Conference (OFC/NFOEC) in Anaheim, Calif. March 17-21.

In the system, Nyquist-shaped 400Gb/s signals with tunable spectral efficiency were generated using modulated subcarriers. Eight 100 GHz-spaced, 400 Gb/s wavelength-division-multiplexed signals were combined and then transmitted over a re-circulating transmission test platform consisting of 100-km fiber spans.

Using the new modulation technique and a new low-loss, large-effective area fiber from OFS Labs, the team transmitted the signals over a record-breaking 12,000 kilometers (roughly 7500 miles)—surpassing their own previous distance record (using the 50 gigahertz-grid) by more than 9000 km.

This shows an experimental setup consisting of the 495Gb/s PM-QPSK-8QAM transmitter, the transmission line system implemented in a recirculating loop, and the digital coherent receiver. WDM: wavelength division multiplexer; DSP: digital signal processing; DAC: digital to analog converter; ILF: interleave filter; IQ MOD: in-phase and quadrature modulator; POL MUX: polarization multiplexer; OA: optical amplifier; LO: local oscillator; O/E: optical to electrical converter; ULA: ultra-large area; ADC: analog to digital converter. Credit: AT&T Labs

"This result not only represents a reach increase by a factor of 2.5 for 100 GHz-spaced 400 G-class WDM systems, it also sets a new record for the product of spectral efficiency and distance," says Zhou. Compared to modulation techniques currently used, he says, "our method has the unique capability to allow tuning of the modulation spectral efficiency to match the available channel bandwidth and maximize the reach, while maintaining tolerance to fiber nonlinearities and laser phase noise, both of which are major factors limiting performance for high-speed optical systems."

Explore further: Internet TV case: US justices skeptical, concerned

More information: Zhou's presentation at OFC/NFOEC, entitled "12,000km Transmission of 100GHz Spaced, 8x495-Gb/s PDM Time-Domain Hybrid QPSK-8QAM Signals," will take place Tuesday, March 19 at 3 p.m. in the Anaheim Convention Center.

Provided by The Optical Society

5 /5 (9 votes)

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User comments : 9

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Frostiken
1 / 5 (4) Mar 12, 2013
Sorry, who is debating this? "Network carriers"? Which ones? And what do you mean by 'today's optical grid networks'?

Because if you're referring to the United States I don't know why any 'network carriers' would be talking about this, simply because none of them care. Every major ISP has made it clear they don't think anyone needs internet faster than a couple megabits a second. They're eating up 95% profit margins and refuse to improve / invest in new infrastructure and services, because they exist in a zero-competition bubble and it would cost money to do that (which would cut into their exhorbitant profits we pay for overpriced internet of inferior quality to just about all of Europe).

So I guess this article is cool, so us Americans can think about how great the internet in Germany is going to be, while less than half our country has access to even cable, a decent chunk are on terrible DSL, and some are even on dial-up, while only about 0.5% have fiber of any kind.
baudrunner
5 / 5 (1) Mar 12, 2013
Network carriers do care, because increased capacity on minimal infrastructure is very tempting.
joeytron9000
5 / 5 (1) Mar 12, 2013
@Frostken - Seriously? This isn't about getting your torrents to hit 400G/s, this is about creating a fast, robust, global network. This is awesome news for anyone who understands networks.
VendicarE
1 / 5 (2) Mar 12, 2013
Americans will never see this technology.

Network providers in the U.S. are the content providers, and they have a negative incentive to upgrade any competition that will reduce the value of the content they provide.

trekgeek1
5 / 5 (1) Mar 12, 2013
Americans will never see this technology.

Network providers in the U.S. are the content providers, and they have a negative incentive to upgrade any competition that will reduce the value of the content they provide.



Then explain the development of current network infrastructure. For instance, Verizon has increased their speed exponentially over the last 10 years in my area. They have also begun offering content via their FiOS service, which provides TV and internet. By your reasoning, they wouldn't have done this because access to Amazon prime, Netflix, Hulu, and other services would compete with their TV service. How do you account for increased network speeds across regions and companies over the past two decades? There is no doubt network speeds are faster than ten years ago, which were faster than ten years before that.
baudrunner
4.5 / 5 (2) Mar 12, 2013
@trekgeek1: you're right. Odd how the spirit of competition seems to have swooshed right by their heads. Naturally, we all want faster and faster, and the providers are going to be tripping over each other to get our business.
VENDItardE
1 / 5 (3) Mar 13, 2013
Americans will never see this technology.

Network providers in the U.S. are the content providers, and they have a negative incentive to upgrade any competition that will reduce the value of the content they provide.


u r a retard
alfie_null
not rated yet Mar 13, 2013
Then explain the development of current network infrastructure. For instance, Verizon has increased their speed exponentially over the last 10 years in my area. They have also begun offering content via their FiOS service, which provides TV and internet. By your reasoning, they wouldn't have done this because access to Amazon prime, Netflix, Hulu, and other services would compete with their TV service. How do you account for increased network speeds across regions and companies over the past two decades? There is no doubt network speeds are faster than ten years ago, which were faster than ten years before that.

You're answering the wrong question. The question you should ask is: Are Americans getting the best value for the money they pay to their providers?
Frostiken
1 / 5 (1) Mar 14, 2013
@baudrunner - You obviously missed the point where the vast majority of internet subscribers have no competition to even chose from. You get:

1 DSL provider
1 Cable provider
Dial up

And those are most people's choices.

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