The various paths to co-packaged optics

Near package optics has emerged as companies have encountered the complexities of co-packaged optics. It should not be viewed as an alternative to co-packaged optics but rather a pragmatic approach for its implementation.

Co-packaged optics will be one of several hot topics at the upcoming OFC show in March.

Placing optics next to silicon is seen as the only way to meet the future input-output (I/O) requirements of ICs such as Ethernet switches and high-end processors.

Brad Booth

For now, pluggable optics do the job of routing traffic between Ethernet switch chips in the data centre. The pluggable modules sit on the switch platform’s front panel at the edge of the printed circuit board (PCB) hosting the switch chip.

But with switch silicon capacity doubling every two years, engineers are being challenged to get data into and out of the chip while ensuring power consumption does not rise.

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Intel sets a course for scalable optical input-output

• Intel is working with several universities to create building-block circuits to address its optical input-output (I/O) needs for the next decade-plus.

• By 2024 the company wants to demonstrate the technologies achieving 4 terabits-per-second (Tbps) over a fibre at 0.25 picojoules-per-bit (pJ/b).

Intel has teamed up with seven universities to address the optical I/0 needs for several generations of upcoming products.

The initiative, dubbed the Intel Research Center for Integrated Photonics for Data Centre Interconnects, began six months ago and is a three-year project.

No new location is involved, rather the research centre is virtual with Intel funding the research. By setting up the centre, Intel’s goal is to foster collaboration between the research groups.

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Preparing for a post-pluggable optical module world

Part 1: OIF: ELSFP, XSR+, and CEI-112G-Linear

The OIF is working on several electrical and optical specifications as the industry looks beyond pluggable optical transceivers.

One initiative is to specify the external laser source used for co-packaged optics, dubbed the External Laser Small Form Factor Pluggable (ELSFP) project. 

Nathan Tracy

Industry interest in co-packaged optics, combining an ASIC and optical chiplets in one package, is growing as it becomes increasingly challenging and costly to route high-speed electrical signals between a high-capacity Ethernet switch chip and the pluggable optics on the platform’s faceplate.

The OIF is also developing 112-gigabit electrical interfaces to address not just co-packaged optics but also near package optics and the interface needs of servers and graphics processor units (GPUs).

Near package optics also surrounds the ASIC with optical chiplets. But unlike co-packaged optics, the ASIC and chiplets are placed on a high-performance substrate located on the host board.

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First co-packaged optics switches set for next year

Ranovus says two of its lead customers will deploy co-packaged optics next year.

They will deploy 25.6-terabit Ethernet switch chips but these will be proof-of-concept designs rather than volume deployments.

Hamid ArabzadehThe deployments will be used to assess the software and gain experience with their maintenance including replacing optics if needed.

“I do think 2024 is going to be the volume year,” says Hamid Arabzadeh, CEO of Ranovus, who expects to announce the customers before the year-end.

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Marvell’s latest acquisition: switch-chip firm Innovium

• Innovium will be Marvell's fifth acquisition in four years  

Marvell is buying switch-chip maker, Innovium, for $1.1 billion to bolster its revenues from the lucrative data centre market.

Nariman Yousefi

The combination of Innovium with Inphi, Marvell’s most recent $10 billion acquisition, will enable the company to co-package optics alongside the high-bandwidth, low-latency switch chips.

“Inphi has quite a bit of experience shipping silicon photonics with the ColorZ and ColorZ II [modules],” says Nariman Yousefi, executive vice president, automotive, coherent DSP and switch group at Marvell. “And we have programmes inside the company to do co-packaged optics as well.”

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Intel details its 800-gigabit DR8 optical module

The company earmarks 2023 for its first co-packaged optics product

Intel is sampling an 800-gigabit DR8 in an OSFP pluggable optical module, as announced at the recent OFC virtual conference and show.

Robert Blum“It is the first time we have done a pluggable module with 100-gigabit electrical serdes [serialisers/ deserialisers],” says Robert Blum, Intel’s senior director, marketing and new business. “The transition for the industry to 100-gigabit serdes is a big step.”

The 800-gigabit DR8 module has eight electrical 100-gigabit interfaces and eight single-mode 100-gigabit optical channels in each transmission direction.

The attraction of the single-module DR8 design, says Blum, is that it effectively comprises two 400-gigabit DR4 modules. “The optical interface allows you the flexibility that you can break it out into 400-gigabit DR4,” says Blum. “You can also do single 100-gigabit breakouts or you can do 800-gigabit-to-800-gigabit traffic.”

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COBO adds co-packaged optics to its agenda

The Consortium of On-Board Optics (COBO) is progressing with its work to create specifications for co-packaged optics.

The decision to address co-packaged optics by an organisation established to promote on-board optics reflects the significant industry interest co-packaged optics has gained in the last year.

So says Brad Booth, director, leading edge architecture pathfinding team in Azure hardware systems and infrastructure at Microsoft.

Source: COBO

The COBO work also complements that of the OIF which has set up its own co-packaged optics framework. 

“We have a different collection of members [to the OIF],” says Booth. “Our members are very strong on optical connectivity and materials whereas the OIF is known for its electrical interface work and module activities like 400ZR.”

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