800G MSA defines PSM8 while eyeing 400G’s progress

A key current issue regarding data centres is forecasting the uptake of 400-gigabit optics.

If a rapid uptake of 400-gigabit optics occurs, it will also benefit the transition to 800-gigabit modules. But if the uptake of 400-gigabit optics is slower, some hyperscalers could defer and wait for 800-gigabit pluggables instead.

So says Maxim Kuschnerov, a spokesperson for the 800G Pluggable MSA (multi-source agreement).

Maxim Kuschnerov

The 800G MSA has issued its first 800-gigabit pluggable specification.

Dubbed the PSM8, the design uses the same components as 400-gigabit optics, doubling capacity in the same QSFP-DD pluggable form factor.

“Four-hundred-gigabit modules hitting volume is crucially important because the 800-gigabit specification leverages 400-gigabit components,” says Kuschnerov. “The more 400-gigabit is delayed, it impacts everything that comes after.”

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Telecoms embraces 400ZR optics for IP-over-DWDM

Verizon Media has trialled 400-gigabit coherent pluggable optics to improve the delivery of video content to subscribers.

Tomas Maj

Verizon Media added a 400ZR QSFP-DD module from Inphi to a switch already using 100-gigabit optics to upgrade its content delivery network.

Adding dense wavelength-division multiplexing (DWDM) optics to a switch enables it to send IP traffic (IP-over-DWDM) directly without needing a separate DWDM data centre interconnect box and additional client-side optics to link the two platforms (see diagram).

“Verizon Media, showing leadership outside the hyperscalers, is moving to IP-over-DWDM,” says Tomas Maj, senior director, marketing, optical interconnect at Inphi. “It shows the maturity of the ecosystem and the confidence of more and more operators in IP-over-DWDM and 400ZR.”

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Telecoms' innovation problem and its wider cost

Imagine how useful 3D video calls would have been this last year.

The technologies needed - a light field display and digital compression techniques to send the resulting data across a network - do exist but practical holographic systems for communication remain years off.

Source: Accelerating Innovation in the Telecommunications Arena

But this is just the sort of application that telcos should be pursuing to benefit their businesses.

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Nokia shares its vision for cost-reduced coherent optics

Nokia explains why coherent optics will be key for high-speed short-reach links and shares some of its R&D activities. The latest in a series of articles addressing what next for coherent.

Part 3: Reducing cost, size and power 

Coherent optics will play a key role in the network evolution of the telecom and webscale players.

The modules will be used for ever-shorter links to enable future cloud services delivered over 5G and fixed-access networks.

Tod Sizer

The first uses will be to link data centres and support traffic growth at the network edge.

This will be followed with coherent optics being used within the data centre, once traffic growth requires solutions that 4-level pulse-amplitude modulation (PAM4) direct-detect optics can no longer address.

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Acacia targets access networks with coherent QSFP-DD

• Acacia Communications has announced a 100-gigabit coherent QSFP-DD pluggable module.
• The module is the first of several for aggregation in the access network.

The second article addressing what next for coherent

Part 2: 100-gigabit coherent QSFP-DD

Acacia Communications has revisited 100-gigabit coherent but this time for access rather than metro networks.

Acacia’s metro 100-gigabit coherent pluggable product, a CFP, was launched in 2014. The pluggable has a reach from 80km to 1,200km and consumes 24-26W.

Tom Williams

The latest coherent module is the first QSFP-DD to support a speed lower than the 400-gigabit 400ZR and ZR+ applications that have spurred the coherent pluggable market. 

The launching of a 100-gigabit coherent QSFP-DD reflects a growing need to aggregate 10 Gigabit Ethernet (GbE) links at the network edge as 5G and fibre are deployed.

“The 10GbE links in all the different types of access networks highlight a need for a cost-effective way to do this aggregation,” says Tom Williams, vice president of marketing at Acacia.

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Is traffic aggregation the next role for coherent?

Ciena and Infinera have each demonstrated the transmission of 800-gigabit wavelengths over near-1,000km distances, continuing coherent's marked progress. But what next for coherent now that high-end optical transmission is approaching the theoretical limit? Can coherent compete over shorter spans and will it find new uses?

The first of several articles addressing what next for coherent.

Part 1: XR Optics

“I’m going to be a bit of a historian here,” says Dave Welch, when asked about the future of coherent.

Interest in coherent started with the idea of using electronics rather than optics to tackle dispersion in fibre. Using electronics for dispersion compensation made optical link engineering simpler.

Dave Welch

Coherent then evolved as a way to improve spectral efficiency and reduce the cost of sending traffic, measured in gigabit-per-dollar.

“By moving up the QAM (quadrature amplitude modulation) scale, you got both these benefits,” says Welch, the chief innovation officer at Infinera.

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Open Eye MSA gets webscale attention

Microsoft has trialled optical modules that use signalling technology developed by the Open Eye Consortium.

The webscale player says optical modules using the Open Eye’s analogue 4-level pulse-amplitude modulation (PAM-4) technology consume less power than modules with a PAM-4 digital signal processor (DSP).

“Open Eye has shown us at least an ability that we can do better on power,” says Brad Booth, director, next cloud system architecture, Azure hardware systems and infrastructure at Microsoft, during an Open Eye webinar.

Brad BoothOptical module power consumption is a key element of the total power budget of data centres that can have as many as 100,000 servers and 50,000 switches.

“You want to avoid running past your limit because then you have to build another data centre,” says Booth.

But challenges remain before Open Eye becomes a mainstream technology, says Dale Murray, principal analyst at market research firm, LightCounting.

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