Heading off the capacity crunch

Feature - Part 1: Capacity limits and remedies

Improving optical transmission capacity to keep pace with the growth in IP traffic is getting trickier. 

Engineers are being taxed in the design decisions they must make to support a growing list of speeds and data modulation schemes. There is also a fissure emerging in the equipment and components needed to address the diverging needs of long-haul and metro networks. As a result, far greater flexibility is needed, with designers looking to elastic or flexible optical networking where data rates and reach can be adapted as required.

Figure 1: The green line is the non-linear Shannon limit, above which transmission is not possible. The chart shows how more bits can be sent in a 50 GHz channel as the optical signal to noise ratio (OSNR) is increased. The blue dots closest to the green line represent the performance of the WaveLogic 3, Ciena's latest DSP-ASIC family. Source: Ciena.

But perhaps the biggest challenge is only just looming. Because optical networking engineers have been so successful in squeezing information down a fibre, their scope to send additional data in future is diminishing. Simply put, it is becoming harder to put more information on the fibre as the Shannon limit, as defined by information theory, is approached.

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Cyan's stackable optical rack for data centre interconnent

Demand for high-capacity links between data centres is creating a new class of stackable optical platform from equipment makers. Cyan has unveiled the N-Series, what it calls an open hyperscale transport platform. "It is a hardware and software system specifically for data centre interconnect," says Joe Cumello, Cyan's chief marketing officer. Cyan's announcement follows on from Infinera, which detailed its Cloud Xpress platform last year.

"The drivers for these [data centre] guys every day of the week is lowest cost-per-gigabit"

Joe Cumello

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Photonics and optics: interchangeable yet different

Why is it fibre-optics, and why is it not the semiconductor photonic amplifier? It is all to do with a systems perspective versus a device perspective. An industry debate about optics and photonics.

Many terms in telecom are used interchangeably. Terms gain credibility with use but over time things evolve. For example, people understand what is meant by the term carrier [of traffic] or operator [of a network] and even the term incumbent [operator] even though markets are now competitive and 'telephony' is no longer state-run.

"For me, optics is the equivalent of electrical, and photonics is the equivalent of electronics - LSI, VLSI chips and the like" - Mehdi Asghari

Operators - ex-incumbents or otherwise - also do more that oversee the network and now provide complex services. But of course they differ from service providers such as the over-the-top players [third-party providers delivering services over an operator's infrastructure, rather than any theatrical behaviour] or internet content providers. 

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Infinera introduces flexible grid 500G super-channel ROADM

Infinera has unveiled a flexible grid, reconfigurable optical add/drop multiplexer (ROADM) to complement its DTN-X optical networking platform.

An example showing the impact of a 500G super-channel ROADM node. Source: Infinera

"The FlexROADM will open up the Tier-1 operators in a way Infinera has not been able to do before," says Dana Cooperson, vice president, network infrastructure at market research firm, Ovum. "The DTN-X was necessary but not sufficient; the ROADM is the last piece."

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Books in 2013 - Part 2

Alcatel-Lucent's President of Bell Labs and CTO, Marcus Weldon, on the history and future of Bell Labs, and titles for Christmas; Steve Alexander, CTO of Ciena, on underdogs, connectedness, and deep-sea diving; and Dave Welch, President of Infinera on how people think, and an extraordinary WWII tale: the second part of Books 2013.  

Steve Alexander, CTO of Ciena

David and Goliath: Underdogs, Misfits, and the Art of Battling Giants by Malcolm Gladwell. 

I’ve enjoyed some of Gladwell’s earlier works such as The Tipping Point and Outliers: The Story of Success. You often have to read his material with a bit of a skeptic's eye since he usually deals with people and events that are at least a standard deviation or two away from whatever is usually termed “normal.”

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SDN starts to fulfill its network optimisation promise

Infinera, Brocade and ESnet demonstrate the use of software-defined networking to provision and optimise traffic across several networking layers.

Infinera, Brocade and network operator ESnet are claiming a first in demonstrating software-defined networking (SDN) performing network provisioning and optimisation using platforms from more than one vendor.

Mike Capuano, Infinera

The latest collaboration is one of several involving optical vendors that are working to extend SDN to the WAN. ADVA Optical Networking and IBM are working to use SDN to connect data centres, while Ciena and partners have created a test bed to develop SDN technology for the WAN.

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Infinera speeds up network restoration

• Claimed to be the only hardware implementation of the Shared Mesh Protection protocol
• Provides network-wide protection against multiple network failures
• The chip is already within the DTN-X system; protocol will be activated this year

Pravin Mahajan, Infinera

Infinera has developed a chip to speed up network restoration following faults.

The chip implements the Shared Mesh Protection (SMP) protocol being developed by the International Telecommunication Union (ITU) and the Internet Engineering Task Force (IETF) and Infinera believes it is the only vendor with hardware acceleration of the protocol.

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