Acacia eyes pluggables as it demos its AC1200 module

The emerging market opportunity for pluggable coherent modules is causing companies to change their strategies. 

Ciena is developing and plans to sell its own coherent modules. And now Acacia Communications, the coherent technology specialist, says it is considering changing its near-term coherent digital signal processor (DSP) roadmap to focus on coherent pluggables for data centre interconnect and metro applications. 

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400ZR will signal coherent’s entry into the datacom world

• 400ZR will have a reach of 80km and a target power consumption of 15W 
• The coherent interface will be available as a pluggable module that will link data-centre switches across sites    
• Huawei expects first modules to be available in the first half of 2020
• At OFC, Huawei announced its own 250km 400-gigabit single-wavelength coherent solution that is already being shipped to customers

Coherent optics will finally cross over into datacom with the advent of the 400ZR interface.  So claims Maxim Kuschnerov, senior R&D manager at Huawei.

Maxim Kuschnerov400ZR is an interoperable 400-gigabit single-wavelength coherent interface being developed by the Optical Internetworking Forum (OIF) {add link}.

The 400ZR will be available as a pluggable module and as on-board optics using the COBO specification {add link}. The IEEE is also considering a proposal to adopt the 400ZR specification, initially for the data-centre interconnect market. “Once coherent moves from the OIF to the IEEE, its impact in the marketplace will be multiplied,” says Kuschnerov. 

But developing a 400ZR pluggable represents a significant challenge for the industry. “Such interoperable coherent 16-QAM modules won’t happen easily,” says Kuschnerov. “Just look at the efforts of the industry to have PAM-4 interoperability, it is a tremendous step up from on-off keying.” 

Despite the challenges, 400ZR products are expected by the first half of 2020.

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COBO issues industry’s first on-board optics specification

• COBO modules supports 400-gigabit and 800-gigabit data rates   
• Two electrical interfaces have been specified: 8 and 16 lanes of 50-gigabit PAM-4 signals. 
• There are three module classes to support designs ranging from client-slide multi-mode to line-side coherent optics. 
• COBO on-board optics will be able to support 800 gigabits and 1.6 terabits once 100-gigabit PAM-4 electrical signals are specified. 

Source: COBO

Interoperable on-board optics has moved a step closer with the publication of the industry’s first specification by the Consortium for On-Board Optics (COBO).

COBO has specified modules capable of 400-gigabits and 800-gigabits rates. The designs will also support 800-gigabit and 1.6-terabit rates with the advent of 100-gigabit single-lane electrical signals. 

“Four hundred gigabits can be solved using pluggable optics,” says Brad Booth, chair of COBO and principal network architect for Microsoft’s Azure Infrastructure. “But if I have to solve 1.6 terabits in a module, there is nothing out there but COBO, and we are ready.”

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COBO targets year-end to complete specification

Part 3: 400-gigabit on-board optics

• COBO will support 400-gigabit and 800-gigabit interfaces 
• Three classes of module have been defined, the largest supporting at least 17.5W 

The Consortium for On-board Optics (COBO) is scheduled to complete its module specification this year.

A draft specification defining the mechanical aspects of the embedded optics - the dimensions, connector and electrical interface - is already being reviewed by the consortium’s members.

Brad Booth“The draft specification encompasses what we will do inside the data centre and what will work for the coherent market,” says Brad Booth, chair of COBO and principal network architect for Microsoft’s Azure Infrastructure.

COBO was established in 2015 to create an embedded optics multi-source agreement (MSA). On-board optics have long been available but until now these have been proprietary solutions. 

“Our goal [with COBO] was to get past that proprietary aspect,” says Booth. “That is its true value - it can be used for optical backplane or for optical interconnect and now designers will have a standard to build to.” 

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The OIF’s 400ZR coherent interface starts to take shape

Part 2: Coherent developments

The Optical Internetworking Forum’s (OIF) group tasked with developing two styles of 400-gigabit coherent interface is now concentrating its efforts on one of the two.

When first announced last November, the 400ZR project planned to define a dense wavelength-division multiplexing (DWDM) 400-gigabit interface and a single wavelength one. Now the work is concentrating on the DWDM interface, with the single-channel interface deemed secondary. 

Karl Gass"It [the single channel] appears to be a very small percentage of what the fielded units would be,” says Karl Gass of Qorvo and the OIF Physical and Link Layer working group vice chair, optical, the group responsible for the 400ZR work.

The likelihood is that the resulting optical module will serve both applications. “Realistically, probably both [interfaces] will use a tunable laser because the goal is to have the same hardware,” says Gass.   

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Coherent optics players target the network edge for growth

Part 1: Coherent developments

The market for optical links for reaches between 10km and 120km is emerging as a fierce battleground between proponents of coherent and direct-detection technologies. 

Interest in higher data rates such as 400 gigabits is pushing coherent-based optical transmission from its traditional long-distance berth to shorter-reach applications. “That tends to be where the growth for coherent has come from as it has migrated from long-haul to metro,” says Tom Williams, senior director of marketing at Acacia Communications, a coherent technology supplier. 

Source: Acacia Communications, Gazettabyte

Williams points to the Optical Internetworking Forum’s (OIF) ongoing work to develop a 400-gigabit link for data centre interconnect. Dubbed 400ZR, the project is specifying an interoperable coherent interface that will support dense wavelength-division multiplexing (DWDM) links for distances of at least 80km.

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