The future of optical I/O is more parallel links

Chris Cole has a lofty vantage point regarding how optical interfaces will likely evolve.

As well as being an adviser to the firm II-VI, Cole is Chair of the Continuous Wave-Wavelength Division Multiplexing (CW-WDM) multi-source agreement (MSA). 

Chris Cole

The CW-WDM MSA recently published its first specification document defining the wavelength grids for emerging applications that require eight, 16 or even 32 optical channels.

And if that wasn’t enough, Cole is also the Co-Chair of the OSFP MSA, which will standardise the OSFP-XD (XD standing for extra dense) 1.6-terabit pluggable form factor that will initially use 16, 100 gigabits-per-second (Gbps) electrical lanes. And when 200Gbps electrical input-output (I/O) technology is developed, OSFP-XD will become a 3.2-terabit module. 

Directly interfacing with 100Gbps ASIC serialiser/ deserialiser (serdes) lanes means the 1.6-terabit module can support 51.2-terabit single rack unit (1RU) Ethernet switches without needing 200Gbps ASIC serdes required by eight-lane modules like the OSFP.

“You might argue that it [the OSFP-XD] is just postponing what the CW-WDM MSA is doing,” says Cole. “But I’d argue the opposite: if you fundamentally want to solve problems, you have to go parallel.”

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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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ADTRAN-ADVA's metro-access play

ADTRAN and ADVA have agreed to merge after a long courtship.

The two CEOs have spoken regularly over the years but several developments spurred them to act.

Tom Stanton, ADTRAN CEO

The merger combines ADTRAN’s expertise in access technologies with ADVA’s metro wavelength-division multiplexing (WDM) know-how to create a ‘metro-core-to-door’ company with revenues of $1.2 billion.

As such, the merger promises to double their size and networking skills. Yet the stock market appeared underwhelmed by the announcement, with ADTRAN’s shares down 16% for the rest of the week after the deal was announced. 

Market research analysts, however, are more upbeat.

“ADTRAN and ADVA have a better path forward together than separately,” said John Lively, principal analyst at LightCounting Market Research, in a research note.

The deal is expected to close in the second or third quarter of 2022 but only after several hurdles are overcome in what is described as a complex deal.

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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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ADVA’s 800-gigabit CoreChannel causes a stir

ADVA’s latest addition to its FSP 3000 TeraFlex platform provides 800-gigabit optical transmission. But the announcement has caused a kerfuffle among its optical transport rivals.

ADVA’s TeraFlex platform supports various coherent optical transport sleds, a sled being a pluggable modular unit that customises a platform’s functionality.

Stephan RettenbergerThe coherent sleds use Cisco’s (formerly Acacia Communication’s) AC1200 optical engine. Cisco completed the acquisition of Acacia in March.

The AC1200 comprises a 16nm CMOS Pico coherent digital signal processor (DSP) that supports two wavelengths, each up to 600-gigabit, and two photonic integrated circuits (PICs), for a maximum capacity of 1.2 terabits.

The latest sled from ADVA, dubbed CoreChannel, supports an 800-gigabit stream in a single channel.

ADVA states in its press release that the CoreChannel uses “140 gigabaud (GBd) sub-carrier technology” to deliver 800-gigabit over distances exceeding 1,600km.

This, the company says, improves reach by over 50 per cent compared with state-of-the-art 95GBd symbol rate coherent technologies.

It is these claims that have its rivals reacting.

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Turning to optical I/O to open up computing pinch points

Getting data in and out of chips used for modern computing has become a key challenge for designers.

Hugo Saleh

A chip may talk to a neighbouring device in the same platform or to a chip across the data centre.

The sheer quantity of data and the reaches involved - tens or hundreds of meters - is why the industry is turning to optical for a chip’s input-output (I/O).

It is this technology transition that excites Ayar Labs.

The US start-up showcased its latest TeraPHY optical I/O chiplet operating at 1 terabit-per-second (Tbps) during the OFC virtual conference and exhibition held in June.

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Infinera's XR optics pluggable plans

Infinera’s coherent pluggables for XR optics will also address the company’s metro needs.

Coherent pluggables now dominate the metro market where embedded designs account for just a fifth of all ports, says Infinera.

Robert Shore

“As we grow our metro business, we need our own pluggables if we want to be cost-competitive,” says Robert Shore, senior vice president of marketing at Infinera.

Infinera’s family of pluggables implementing the XR optics concept is dubbed ICE-XR.

XR optics splits a coherent optical signal into Nyquist sub-carriers, each carrying a data payload. Twenty-five gigabits will likely be the sub-carrier capacity chosen.

XR optics can be used for point-to-point links where all the sub-carriers go to the same destination. But the sub-carriers can also be steered to different destinations, similar to how breakout cables are used in the data centre.

With XR optics, a module can talk to several lower-speed ones in a point-to-multipoint arrangement. This enables optical feeds to be summed, ideal for traffic aggregation applications such as access and 5G.

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