Optical networking: The next 10 years

Feature - Part 2: Optical networking R&D

Predicting the future is a foolhardy endeavour, at best one can make educated guesses.

Ioannis Tomkos is better placed than most to comment on the future course of optical networking. Tomkos, a Fellow of the OSA and the IET at the Athens Information Technology Centre (AIT), is involved in several European research projects that are tackling head-on the challenges set to keep optical engineers busy for the next decade.

“We are reaching the total capacity limit of deployed single-mode, single-core fibre,” says Tomkos. “We can’t just scale capacity because there are limits now to the capacity of point-to-point connections.”

Source: Infinera 

The industry consensus is to develop flexible optical networking techniques that make best use of the existing deployed fibre. These techniques include using spectral super-channels, moving to a flexible grid, and introducing ‘sliceable’ transponders whose total capacity can be split and sent to different locations based on the traffic requirements.

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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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NeoPhotonics to expand its tunable laser portfolio

Part 1: Tunable lasers

NeoPhotonics will become the industry's main supplier of narrow line-width tunable lasers for high-speed coherent systems once its US $17.5 million acquisition of Emcore's tunable laser business is completed. Gazettabyte spoke with Ferris Lipscomb of NeoPhotonics about Emcore's external cavity laser and the laser performance attributes needed for metro and long haul.   

Key specifications and attributes of Emcore's external cavity laser and NeoPhotonics's DFB laser array. Source: NeoPhotonics.

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G.fast adds to the broadband options of the service providers

Feature: G.fast

Source: Alcatel-Lucent

Competition is commonly what motivates service providers to upgrade their access networks. And operators are being given every incentive to respond. Cable operators are offering faster broadband rates and then there are initiatives such as Google Fiber.

Internet giant Google is planning 1 Gigabit fibre rollouts in up to 34 US cities covering 9 metro areas. The initiative prompted AT&T to issue its own list of 21 cities it is considering to offer a 1 Gigabit fibre-to-the-home (FTTH) service.

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Amplifiers come to the fore to tackle agile network challenges

The growing sophistication of high-speed optical transmission based on 100 Gigabit-plus lightpaths and advanced ROADMs is rekindling interest in amplifier design.

Raman is a signature of the spread of 100 Gig but also the desire of being upgradable to higher bit rates

Per Hansen, II-VI

For the last decade, amplifier designers have been tasked with reducing the cost of Erbium-doped fibre amplifiers (EDFAs). "Now there is a need for new solutions that are more expensive," says Daryl Inniss, vice president and practice leader, components at market research firm, Ovum. "It is no longer just cost-cutting."

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Xtera demonstrates 40 Terabit using Raman amplification

Feature: 100 Gig and Beyond. Part 2

• Xtera's Raman amplification boosts capacity and reach
• 40 Terabit optical transmission over 1,500km in Verizon trial
• 64 Terabit over 1,500km in 2015 using a Raman module operating over 100nm of spectrum  

Herve Fevrier

Optical transport equipment makers continue to research techniques to increase the data carried long distances over a fibre without sacrificing reach. The techniques include signal processing of the transmit signal to cram data-carrying channels closer in the C-band, advanced soft-decision forward error correction (SD-FEC) and receiver signal processing to counter transmission impairments.

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Verizon on 100G+ optical transmission developments

Source: Gazettabyte

Feature: 100 Gig and Beyond. Part 1:

Verizon's Glenn Wellbrock discusses 100 Gig deployments and higher speed optical channel developments for long haul and metro. 

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