Taking a unique angle to platform design

• A novel design based on a vertical line card shortens the trace length between an ASIC and pluggable modules.
• Reducing the trace length improves signal integrity while maintaining the merits of using pluggables.
• Using the vertical line card design will extend for at least two more generations the use of pluggables with Ethernet switches.

The travelling salesperson problem involves working out the shortest route on a round-trip to multiple cities. It's a well-known complex optimisation problem.

Chris Cole

Systems engineers face their own complex optimisation problem just sending an electrical signal between two points, connecting an Ethernet switch chip to a pluggable optical module, for example.

Sending the high-speed signal over the link with sufficient fidelity for its recovery requires considerable electronic engineering design skills. And with each generation of electrical signalling, link distances are getting shorter.

In a paper presented at the recent ECOC show, held in Basel, consultant Chris Cole, working with Yamaichi Electronics, outlined a novel design that shortens the distance between an Ethernet switch chip and the front-panel optics.

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Nokia adds 400G coherent modules across its platforms

Nokia is now shipping its 400-gigabit coherent multi-haul CFP2-DCO. The module exceeds the optical performance of 400ZR and ZR+ coherent pluggables.

Nokia’s CFP2-DCO product follows its acquisition of silicon photonics specialist, Elenion Technologies, in 2020.

Serge Melle

Nokia has combined Elenion’s coherent optical modulator and receiver with its low-power 64-gigabaud (GBd) PSE-Vc coherent digital signal processor (DSP).

Nokia is also adding coherent pluggables across its platform portfolio.

“Not just optical transport and transponder platforms but also our IP routing portfolio as well,” says Serge Melle, director of product marketing, IP-optical networking at Nokia.

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Ethernet Alliance on 800G and the next Ethernet rate

It may have taken the industry five years to get 400 Gigabit Ethernet (GbE) modules shipping, but for Mark Nowell, Advisory Board Chair at the Ethernet Alliance, the long gestation period is understandable given the innovation that has been required.

Mark Nowell

The industry has had to cram complex technology into a small form factor for 400GbE while meeting the requirements of two very different end-customers: webscale players and communications service providers.

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Inphi unveils first 800-gigabit PAM-4 signal processing chip

Inphi has detailed what it claims is the industry’s first digital signal processor (DSP) chip family for 800-gigabit client-side pluggable modules. 

Dubbed Spica, the 4-level pulse-amplitude modulation (PAM-4) DSP family is sampling and is in the hands of customers.

Source: Inphi

The physical-layer company has also announced its third-generation Porrima family of PAM-4 DSPs for 400-gigabit pluggables. 

The Porrima DSP with integrated laser driver has being made using a 7nm CMOS process; until now a 16nm CMOS has been used. Fabricating the chip using the more advanced process will reduce the power consumption of 400-gigabit module designs. 

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Acacia unveils its 400G coherent module portfolio

Acacia Communications has unveiled a full portfolio of 400-gigabit coherent optics and has provided test samples to customers, one being Arista Networks.

Delivering a complete set of modules offers a comprehensive approach to address the next phase of coherent optics, the company says. 

Tom WilliamsThe 400-gigabit coherent designs detailed by Acacia are implemented using the QSFP-DD, OSFP and CFP2 pluggable form factors.

Collectively, the pluggables support three performance categories: the 400ZR standard, OpenZR+ that is backed by several companies, and the coherent optics specification used for the Open ROADM multi-source agreement (MSA). 

“These are challenging specifications,” says Tom Williams, vice president of marketing at Acacia. “Even the 400ZR, where the objective has been to simplify the requirements.” 

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Optical module trends: A conversation with Finisar

Finisar demonstrated recently a raft of new products that address emerging optical module developments. These include: 

• A compact coherent integrated tunable transmitter and receiver assembly 
• 400GBASE-FR8 and -LR8 QSFP-DD pluggable modules and a QSFP-DD active optical cable 
• A QSFP28 100-gigabit serial FR interface 
• 50-gigabit SFP56 SR and LR modules

Rafik Ward, Finisar’s general manager of optical interconnects, explains the technologies and their uses.

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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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