Data centre photonics - an ECOC report

• ECOC 2022 included talks on optical switching and co-packaged optics.
• Speakers discussed optical switching trends and Google's revelation that it has been using optical circuit switching in its data centres.
• Nvidia discussed its latest chips, how they are used to build high-performance computing systems, and why optical input-output will play a critical role.

Co-packaged optics and optical switching within the data centre were prominent topics at the recent ECOC 2022 conference and exhibition in Basel, Switzerland.

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Compute vendors set to drive optical I/O innovation

Part 2: Data centre and high-performance computing trends

Professor Vladimir Stojanovic has an engaging mix of roles.

When he is not a professor of electrical engineering and computer science at the University of California, Berkeley, he is the chief architect at optical interconnect start-up, Ayar Labs.

Professor Vladimir Stojanovic

Until recently Stojanovic spent four days each week at Ayar Labs. But last year, more of his week was spent at Berkeley.

Stojanovic is a co-author of a 2015 Nature paper that detailed a monolithic electronic-photonics technology. The paper described a technological first: how a RISC-V processor communicated with the outside world using optical rather than electronic interfaces. 

It is this technology that led to the founding of Ayar Labs.

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Data centre disaggregation with Gen-Z and CXL

Part 1: CXL and Gen-Z

• The Gen-Z and Compute Express Link (CXL) protocols have been shown working in unison to implement a disaggregated processor and memory system at the recent Supercomputing 21 show.

• The Gen-Z Consortium’s assets are being subsumed within the CXL Consortium. CXL will become the sole industry standard moving forward.

• Microsoft and Meta are two data centre operators backing CXL.

Pity Hiren Patel, tasked with explaining the Gen-Z and CXL networking demonstration operating across several booths at the Supercomputing 21 (SC21) show held in St. Louis, Missouri in November.

Hiren Patel

Not only was Patel wearing a sanitary mask while describing the demo but he had to battle to be heard above cooling fans so loud, you could still be at St. Louis Lambert International Airport.

Gen-Z and CXL are key protocols supporting memory and server disaggregation in the data centre.

The SC21 demo showed Gen-Z and CXL linking compute nodes to remote ‘media boxes’ filled with memory in a distributed multi-node network (see diagram, bottom).

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A voyage around work

The first in a series looking at the experience of work in 2019.

Source: Mark Seery

To land your ideal job, the suggestion is first to find your passion. Indeed, one college in the US promises to guide its students to find their life purpose by teaching them three things: what they are good at, what they are passionate about, and what the world needs.

Assuming you are lucky enough to align all three elements, challenges are still likely. How do you maintain a work-life balance? And what happens over time when, despite having fulfilling, challenging work, part of your creative self remains untapped?

This has been the experience of Mark Seery (pictured below), who was a senior staff member at Juniper Networks, responsible for helping shape the networking company’s strategy.

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Kim Roberts: The 2019 John Tyndall Award winner

A Profile

A conceptualiser, mathematician, furniture maker, prolific inventor, sushi lover, creative spirit, team leader and mentor. These are just some of the descriptors applied to Kim Roberts of Ciena by the people that know him. 

Kim Roberts of Ciena. On the wall are some of his 160 patents while on the screen is an image of a 32-point constellation produced by the WaveLogic Ai coherent modem. Source: Ciena.

Roberts has been awarded the 2019 John Tyndall Award by The Optical Society (OSA) and the IEEE Photonics Society in recognition of his “pioneering contributions to the development of practical coherent communication systems”.

“It is well deserved,” says Seb Savory, who first knew Roberts when they both worked at Nortel and who is now an academic at the University of Cambridge working on joint projects with Ciena. Ciena acquired Nortel in 2010.

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Switch chips not optics set the pace in the data centre

Broadcom is doubling the capacity of its switch silicon every 18-24 months, a considerable achievement given that Moore’s law has slowed down. 

Last December, Broadcom announced it was sampling its Tomahawk 3 - the industry’s first 12.8-terabit switch chip - just 14 months after it announced its 6.4-terabit Tomahawk 2.

Rochan SankarSuch product cycle times are proving beyond the optical module makers; if producing next-generation switch silicon is taking up to two years, optics is taking three, says Broadcom. 

“Right now, the problem with optics is that they are the laggards,” says Rochan Sankar, senior director of product marketing at switch IC maker, Broadcom. “The switching side is waiting for the optics to be deployable.”

The consequence, says Broadcom, is that in the three years spanning a particular optical module generation, customers have deployed two generations of switches. For example, the 3.2-terabit Tomahawk based switches and the higher-capacity Tomahawk 2 ones both use QSFP28 and SFP28 modules. 

In future, a closer alignment in the development cycles of the chip and the optics will be required, argues Broadcom.

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Will white boxes predominate in telecom networks?

Will future operator networks be built using software, servers and white boxes or will traditional systems vendors with years of network integration and differentiation expertise continue to be needed? 

AT&T’s announcement that it will deploy 60,000 white boxes as part of its rollout of 5G in the U.S. is a clear move to break away from the operator pack.

The service provider has long championed network transformation, moving from proprietary hardware and software to a software-controlled network based on virtual network functions running on servers and software-defined networking (SDN) for the control switches and routers.

Glenn WellbrockNow, AT&T is going a stage further by embracing open hardware platforms - white boxes - to replace traditional telecom hardware used for data-path tasks that are beyond the capabilities of software on servers.       

For the 5G deployment, AT&T will, over several years, replace traditional routers at cell and tower sites with white boxes, built using open standards and merchant silicon.

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