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EE Web – 112G Digs in at DesignCon 2019

112G serial links have moved out of the lab and onto the exhibit floor. 56G ramps up while 28G goes mainstream.

By Martin Rowe, EE Web, 

Last year at DesignCon 2018, we witnessed high-speed digital designs that moved past 56 Gbits/s (56G) and onto 112 Gbits/s (112G). This year, DesignCon 2019 brought numerous demonstrations of 112G as the connectors and cables caught up with the silicon. While still appearing in technical papers and panels, 112G has certainly moved into the exhibit hall. Meanwhile, 56G has matured and is now a complete ecosystem.

When it comes to signal integrity and high-speed signals, transmission lengths certainly matter, especially with electrical signals over copper connections. Yes, optical transmission is an option, but nobody wants to pay for it. At a panel session on Jan. 31, OIF board president Nathan Tracy presented the table shown in Figure 1 that describes five OIF standards for different electrical transmission lengths.

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Figure 1: The Optical Internetworking Forum has created standards for 112-Gbit/s copper connections. (Source: Optical Internetworking Forum and DesignCon)
Given a rule of thumb of 0.1 dB/in./GHz of insertion loss (Figure 2), PCB traces of, say, 10 inches are simply too long. That’s where cables that jump over PCBs have become popular.

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Figure 2: Cable assemblies jump over PCBs to reduce insertion loss. (Source: Optical Internetworking Forum, Broadcom, and DesignCon)
Connectors for 112G took several forms at DesignCon, depending on the length of the transmission. For chip-to-chip or chip-to-module distances, sending 112G four-level pulse-amplitude modulation (PAM4) signals (28 GHz) over PCB traces results in excessive insertion loss. To get past that restriction, several connector companies have developed cable assemblies that jump over sections of boards.

Read more here: https://www.eeweb.com/profile/martin-rowe-2/articles/112g-digs-in-at-designcon-2019

 

OIF Experts to Provide CEI-112G Project Update at DesignCon

Expert panel will provide an update on the multiple interfaces being defined by OIF including CEI-112G MCM, XSR, VSR, MR and LR for 112G

Fremont, Calif.—January 23, 2019 – A panel of OIF experts will present and discuss the ongoing, multi-faceted Common Electrical I/O (CEI)-112G interface effort at this year’s DesignCon being held in Santa Clara, CA January 29-31. “112-Gbps Electrical Interface: An OIF Update on CEI-112G,” is scheduled for Thursday, January 31 at 3:45 pm (local) and will provide an update on the multiple interfaces being defined by OIF including CEI-112G MCM, XSR, VSR, MR and LR. Applications of these 112 Gb/s interfaces include die-to-die, chip-to-module, chip-to-chip and long reach over backplane and cables.

Panel speakers include Brian Holden of Kandou Bus and OIF member; Cathy Liu of Broadcom Inc. and OIF Board Member; Steve Sekel of Keysight Technologies and OIF PLL Interoperability Working Group Chair and Nathan Tracy of TE Connectivity and OIF President.

Since 2000, OIF has defined Interoperability Agreements (IA)s for electrical interconnects known as CEI.  CEI is a clause-based document that defines implementation details for interoperable electrical channels initially issued for 6 Gbps, then 11, 28, and 56 and includes definitions for multiple channel implementation topologies and will soon include 112 Gbps clauses. In August of 2016, OIF announced the first CEI-112G project in an overall effort that has now expanded to five projects.

“Previous CEI development has been highly influential and has been adopted, influenced or adapted by many other high-speed interconnect specifications throughout the industry,” said Tracy. “Given that the CEI-112G generation of high-speed transmitters, receivers and channels will be challenging to define, implement and measure, this panel will provide guidance to where the industry is headed and what the key challenge points are likely to be.”

The CEI-112G IA effort is challenging in signal integrity, implementation complexity and measurement terms. The signals are increasingly vulnerable to channel discontinuities, leading to signal impairment and crosstalk. The switching speed and the density of the available SerDes transistors have not kept pace with other silicon functions, resulting in architectural challenges. Finally, the ability to probe and repeatably capture measurements at these rates with sufficient accuracy and precision is challenging.

Check the status of OIF’s current work in CEI-112G here.

About OIF
OIF is where the optical networking industry’s interoperability work gets done. Celebrating 20 years of effecting progressive change in the industry, OIF represents the dynamic ecosystem of 100+ industry leading network operators, system vendors, component vendors and test equipment vendors, all collaborating to develop interoperable electrical, optical and control solutions that directly impact the industry’s ecosystem and facilitate global connectivity in the open network world. Connect with OIF at @OIForum, on LinkedIn and at http://www.oiforum.com.

 

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