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Entries in PAM-4 (25)

Tuesday
Jul242018

Xilinx delivers 58G serdes and showcases a 112G test chip

In the first of two articles, electrical input-output developments are discussed, focussing on Xilinx’s serialiser-deserialiser (serdes) work for its programmable logic chips. In Part 2, the IMEC nanoelectronics R&D centre’s latest silicon photonics work to enable optical I/O for chips is detailed.

Part 1: Electrical I/O

Processor and memory chips continue to scale exponentially. The electrical input-output (I/O) used to move data on and off such chips scales less well. Electrical interfaces are now transitioning from 28 gigabit-per-second (Gbps) to 56Gbps and work is already advanced to double the rate again to 112Gbps. But the question as to when electrical interfaces will reach their practical limit continues to be debated. 

Gilles Garcia“Some two years ago, talking to the serdes community, they were seeing 100 gigabits as the first potential wall,” says Gilles Garcia, communications business lead at Xilinx. “In two years, a lot of work has happened and we can now demonstrate 112 gigabits [electrical interfaces].”

The challenge of moving to higher-speed serdes is that the reach shortens with each doubling of speed. The need to move greater amounts of data on- and off-chip also has power-consumption implications, especially with the extra circuitry needed when moving from non-return-to-zero signalling to the more complex 4-level pulse-amplitude modulation (PAM-4) scheme.  

PAM-4 is already used for 56-gigabit electrical I/O for such applications as 400 Gigabit Ethernet optical modules and by the leading edge 12.8-terabit capacity switch chips. Having 112-gigabit serdes at least ensures one further generation of switch chips and optical modules but what comes after that is still to be determined. Even if more can be squeezed out of copper, the trace lengths will shorten and optics will continue to get closer to the chip. 

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Monday
Apr162018

COBO issues industry’s first on-board optics specification

  • COBO modules supports 400-gigabit and 800-gigabit data rates   
  • Two electrical interfaces have been specified: 8 and 16 lanes of 50-gigabit PAM-4 signals. 
  • There are three module classes to support designs ranging from client-slide multi-mode to line-side coherent optics. 
  • COBO on-board optics will be able to support 800 gigabits and 1.6 terabits once 100-gigabit PAM-4 electrical signals are specified. 

Source: COBO

Interoperable on-board optics has moved a step closer with the publication of the industry’s first specification by the Consortium for On-Board Optics (COBO).

COBO has specified modules capable of 400-gigabits and 800-gigabits rates. The designs will also support 800-gigabit and 1.6-terabit rates with the advent of 100-gigabit single-lane electrical signals. 

“Four hundred gigabits can be solved using pluggable optics,” says Brad Booth, chair of COBO and principal network architect for Microsoft’s Azure Infrastructure. “But if I have to solve 1.6 terabits in a module, there is nothing out there but COBO, and we are ready.”

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Wednesday
Mar142018

DustPhotonics reveals its optical transceiver play

A start-up that has been active for a year has dropped its state of secrecy to reveal it is already shipping its first optical transceiver product.

The company, DustPhotonics, is backed by private investors and recently received an undisclosed round of funding that will secure the company’s future for the next two years.  

 

Product plans

DustPhotonics' first product is the multi-mode 100m-reach 100GBASE-SR4 QSFP28. The company will launch its first 400-gigabit optical modules later this year. 

Ben Rubovitch

“We probably are going to be one of the first to market with [400-gigabit] QSFP-DD and OSFP multi-mode solutions,” says Ben Rubovitch, CEO of DustPhotonics.

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Sunday
Jan282018

Ayar Labs advances I/O and pens GlobalFoundries deal 

Silicon photonics start-up, Ayar Labs, has entered into a strategic agreement with semiconductor foundry, GlobalFoundries.

Alexandra Wright-GladsteinAyar Labs will provide GlobalFoundries with its optical input-output (I/O) technology. In return, the start-up will gain early access to the foundry’s 45nm CMOS process being tailored for silicon photonics.

GlobalFoundries has also made an investment in the start-up for an undisclosed fee.

“We gain, first and foremost, a close relationship with GlobalFoundries as we qualify our product for customers,” says Alexandra Wright-Gladstein, co-founder and CEO of Ayar Labs. “That will help us speed up availability of our product and have their weight of support behind us.”

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Friday
Oct202017

The many paths to 400 gigabits

The race is on to deliver 400-gigabit optical interfaces in time for the next-generation of data centre switches expected in late 2018.

The industry largely agrees that a four-wavelength 400-gigabit optical interface is most desirable yet alternative designs are also being developed.

Optical module makers must consider such factors as technical risk, time-to-market and cost when choosing which design to back.

Rafik Ward, FinisarUntil now, the industry has sought a consensus on interfaces, making use of such standards bodies as the IEEE to serve the telecom operators.

Now, the volumes of modules used by the internet giants are such that they dictate their own solutions. And the business case for module makers is sufficiently attractive that they are willing to comply.

Another challenge at 400 gigabits is that there is no consensus regarding what pluggable form factor to use. 

“There is probably more technical risk in 400 gigabits than any of the historical data-rate jumps we have seen,” says Rafik Ward, vice president of marketing at Finisar.

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Monday
Oct092017

Oclaro’s 400-gigabit plans

Adam Carter, Oclaro’s chief commercial officer, discusses the company’s 400-gigabit and higher-speed coherent optical transmission plans and the 400-gigabit client-side pluggable opportunity.    

Oclaro showcased its first coherent module that uses Ciena’s WaveLogic Ai digital signal processor at the ECOC show held recently in Gothenburg.

Adam CarterOclaro is one of three optical module makers, the others being Lumentum and NeoPhotonics, that signed an agreement with Ciena earlier this year to use the system vendor’s DSP technology and know-how to bring coherent modules to market. The first product resulting from the collaboration is a 5x7-inch board-mounted module that supports 400-gigabits on a single-wavelength.   

The first WaveLogic Ai-based modules are already being tested at several of Oclaro’s customers’ labs. “They [the module samples] are very preliminary,” says Adam Carter, the chief commercial officer at Oclaro. “The really important timeframe is when we get towards the new year because then we will have beta samples.”

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Monday
Sep252017

The CWDM8 MSA avoids PAM-4 to fast-track 400G  

Another multi-source agreement (MSA) group has been created to speed up the market introduction of 400-gigabit client-side optical interfaces.

The CWDM8 MSA is described by its founding members as a pragmatic approach to provide 400-gigabit modules in time for the emergence of next-generation switches next year. The CWDM8 MSA was announced at the ECOC show held in Gothenburg last week.

Robert BlumThe eight-wavelength coarse wavelength-division multiplexing (CWDM) MSA is being promoted as a low-cost alternative to the IEEE 803.3bs 400 Gigabit Ethernet Task Force’s 400-gigabit eight-wavelength specifications, and less risky than the newly launched 100G Lambda MSA specifications based on four 100-gigabit wavelengths for 400 gigabit.

“The 100G Lambda has merits and we are also part of that MSA,” says Robert Blum, director of strategic marketing and business development at Intel’s silicon photonics product division. “We just feel the time to get to 100-gigabit-per-lambda is really when you get to 800 Gigabit Ethernet.”

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