OIF addresses 800-gigabit coherent interfaces

The OIF has started work on 800-gigabit coherent interfaces, a follow-on to its 400-gigabit 400ZR specification work.

Two requirements are being addressed: an 800-gigabit dense wavelength division (DWDM) interface with a 80-120km span for data centre interconnect, and an unamplified single-channel fixed-wavelength 2-10km coherent link for campuses.

The need for 800 gigabit

Tad Hofmeister

“When we hit that 90 per cent mark on 400ZR, we had people stand up and say: ‘We are ready to start 800ZR’,” says Karl Gass, OIF, physical link layer working group – optical vice-chair.

But completing the work has taken time. “The first 90 per cent of a project takes about half the time and the last 10 per cent takes the other half,” says Gass.

So only in mid-2020 did the OIF’s attention turn to the new standard, starting with determining the use cases.

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DT chooses Nokia for a major optical network upgrade

Deutsche Telekom is redesigning its domestic optical network and has chosen Nokia as its equipment supplier.

“They are re-architecting and rolling out, in a short time, a huge portion of their optical network,” says Kyle Hollasch, (pictured) director of optical portfolio marketing, Nokia. “We are displacing in many parts of the network four different vendors.”

Network architecture

Deutsche Telekom’s legacy mesh-based wavelength-division multiplexing (WDM) network uses equipment from several vendors. In the last decade, Deutsche Telekom also added to the core an IP-optical solution from Cisco Systems.

Now, the CSP is replacing the mesh-WDM network and the Cisco IP-optical core with an OTN-WDM core from Nokia.

“They are unifying their traffic from all of their business services, government services, 5G anyhaul and the core IP network onto one core WDM network,” says Hollasch. 

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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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Nokia targets 400G era with PSE-V coherent DSP launch

Nokia has unveiled its latest coherent digital signal processor (DSP) family, its fifth-generation Photonic Service Engine dubbed the PSE-V. 

Kyle HollaschTwo devices make up the family: the high-end super coherent PSE-Vs and the compact PSE-Vc for use in pluggable modules.

The PSE-Vc chip is already sampling, the PSE-Vs will sample later this year. 

The PSE-Vs, operating at a 90 gigabaud (GBd) symbol rate, supports transmission distances from local data centres to ultra-long-haul and sub-sea networks while the 64GBd PSE-Vc implements the OIF’s 400ZR standard, ZR+ and beyond.

Nokia has also expanded its coherent optics strategy having completed the acquisition of Elenion Technologies. It is now vertically integrated and is offering coherent optics and its DSPs to partners that include module makers and contract manufacturers.

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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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