Has coherent optical transmission run its course?

Feature: Coherent's future

Three optical systems vendors share their thoughts about coherent technology and the scope for further improvement as they look two generations ahead to symbol rates approaching 100 gigabaud   

Optical transmission using coherent detection has made huge strides in the last decade. The latest coherent technology with transmitter-based digital signal processing delivers 25x the capacity-reach of 10-gigabit wavelengths using direct-detection, according to Infinera.

Since early 2016, the optical systems vendors Infinera, Ciena and Nokia have all announced new coherent digital signal processor (DSP) designs. Each new generation of coherent DSP improves the capacity that can be transmitted over an optical link. But given the effectiveness of the latest coherent systems, has most of the benefits already been achieved?

Source: Infinera

“It is getting harder and harder,” admits Kim Roberts, vice president, WaveLogic science at Ciena. “Unlike 10 years ago, there are no factors of 10 available for improvement.”

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Real-time visibility makes optical networking smarter

Part 1: Ciena's Liquid Spectrum

Systems vendors are making optical networks smarter. Their latest equipment, combining intelligent silicon and software hooks, can measure the status of the network and enable dynamic network management.

Ciena recently announced its Liquid Spectrum networking product while Infinera has launched its Instant Network. Both vendors exploit the capabilities of their latest generation coherent DSPs to allow greater network automation and efficiency. The vendors even talk about their products being an important step towards autonomous or cognitive networks.

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Books of the year 2016 - Part 2

More industry figures comment on books read this year. Here are Finisar's Simon Poole's and Ciena's Loudon Blair's recommendations.

Simon Poole, director, new business ventures, Finisar Australia

The highlight of the year in fiction was reading The Shepherds’ Crown, the last of the Discworld novels from the wonderful Terry Pratchett. He, along with his cast of extraordinary characters, including the marvellous Tiffany Aching – a fabulous role model for teenage girls, held up a mirror to the foibles and strengths of our humanity, and will be sorely missed.

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Ciena brings data analytics to optical networking

• Ciena's WaveLogic Ai coherent DSP-ASIC makes real-time measurements, enabling operators to analyse and adapt their networks.     
• The DSP-ASIC supports 100-gigabit to 400-gigabit wavelengths in 50-gigabit increments. 
• The WaveLogic Ai will be used in Ciena’s systems from 2Q 2017.  

Ciena has unveiled its latest generation coherent DSP-ASIC. The device, dubbed WaveLogic Ai, follows Ciena’s WaveLogic 3 family of coherent chips which was first announced in 2012. The Ai naming scheme reflects the company's belief that its latest chipset represents a significant advancement in coherent DSP-ASIC functionality.  

Helen XenosThe WaveLogic Ai is Ciena's first DSP-ASIC to support two baud rates, 35 gigabaud for fixed-grid optical networks and 56 gigabaud for flexible-grid ones. The design also uses advanced modulation schemes to optimise the data transmission over a given link.

Perhaps the most significant development, however, is the real-time network monitoring offered by the coherent DSP-ASIC. The data will allow operators to fine-tune transmissions to adapt to changing networking conditions. 

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OIF starts work on a terabit-plus CFP8-ACO module

The Optical Internetworking Forum (OIF) has started a new analogue coherent optics (ACO) specification based on the CFP8 pluggable module.

The CFP8 is the latest is a series of optical modules specified by the CFP Multi-Source Agreement and will support the emerging 400 Gigabit Ethernet standard.

Karl GassAn ACO module used for optical transport integrates the optics and driver electronics while the accompanying coherent DSP-ASIC residing on the line card.

Systems vendors can thus use their own DSP-ASIC, or a merchant one if they don’t have an in-house design, while choosing the coherent optics from various module makers. The optics and the DSP-ASIC communicate via a high-speed electrical connector on the line card.

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Ciena enhances its 6500 packet-optical transport family

Ciena has upgraded its 6500 family of packet-optical transport platforms with the T-series that supports higher-capacity electrical and optical switching and higher-speed line cards.

"The 6500 T-Series is a big deal as Ciena can offer two different systems depending on what the customer is looking for," says Andrew Schmitt, founder and principal analyst of market research firm, Cignal AI.

Helen XenosIf customers want straightforward transport and the ability to reach a number of different distances, there is the existing 6500 S-series, says Schmitt. The T-series is a system specifically for metro-regional networks that can accommodate multiple traffic types – OTN or packet.

"It has very high density for a packet-optical system and offers pay-as-you-grow with CFP2-ACO [coherent pluggable] modules," says Schmitt.

Ciena says the T-series has been developed to address new connectivity requirements service providers face. Content is being shifted to the metro to improve the quality of experience for end users and reduce capacity on backbone networks. Such user consumption of content is one factor accounting for the strong annual 40 percent growth in metro traffic.

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Ciena shops for photonic technology for line-side edge

Briefing: DWDM developments

Part 3: Acquisitions and silicon photonics

Ciena is to acquire the high-speed photonics components division of Teraxion for $32 million. The deal includes 35 employees and Teraxion’s indium phosphide and silicon photonics technologies. The systems vendor is making the acquisition to benefit its coherent-based packet-optical transmission systems in metro and long-haul networks.

Sterling Perrin

“Historically Ciena has been a step ahead of others in introducing new coherent capabilities to the market,” says Ron Kline, principal analyst, intelligent networks at market research company, Ovum. “The technology is critical to own if they want to maintain their edge.”

“Bringing in-house not everything, just piece parts, are becoming differentiators,” says Sterling Perrin, senior analyst at Heavy Reading.    

Ciena designs its own WaveLogic coherent DSP-ASICs but buys its optical components. Having its own photonics design team with expertise in indium-phosphide and silicon photonics will allow Ciena to develop complete line-side systems, optimising the photonics and electronics to benefit system performance.

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