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Cisco banks on silicon photonics for 2.5D, 3D ICs

Posted: 31 Jan 2013 ?? ?Print Version ?Bookmark and Share

Keywords:DesignCon? silicon photonics? 2.5D silicon interposers? CMOS modulator? software-defined networks?

According to a senior engineering executive in a keynote at DesignCon, Cisco Systems is prototyping silicon photonics using 2.5D silicon interposers. The communications firm is one of a handful of companies trying to maximise the technology to lessen the cost of next-generation networks.

Bill Swift, Cisco's vice president of engineering, stated that the convergence of optical and semiconductor ecosystems will have a huge impact for networking at 40 and 100 Gbit/second and beyond.

Swift showed a rough diagram of a 2.5D chip that included a laser light source, optical lenses and isolators along with what appeared to be a CMOS modulator and multiplexor. "This is stuff we are working on now, and I find it very exciting," he said.

He declined to comment on reports the company will ship this year samples of 100G silicon optical modules based on the LX4 standard. Cisco bought silicon-photonics start-up Lightwire in February 2010 for $271 million.

Lightwire's first generation product used wavelength division multiplexing to put four 25G channels over a single fibre, sources said. Along with start-up Luxtera, it is pushing for use of advanced coding techniques such as eight-level pulse amplitude modulation to get to 50G serial links.

Among Cisco's competitors, Intel announced earlier this month it is shipping engineering samples of 100G silicon photonics modules. Start-ups Luxtera and Kotura plan to ship 100G silicon photonics modules in 2014. Intel is using CMOS for all the major components including the laser light source; Luxtera and Kotura use external lasers. (see Kotura taps CMOS foundry for 100G photonics chips)

Swift said 3D ICs will reduce chip power and accelerate integration. The 2.5D version using silicon interposers is the latest version of a technology that's been around for years, he said.

"In the 1990's, I used a pcb interposer because I got my BGA wrong, now we can use it to put multiple die on silicon," he quipped.


Convergence of CMOS and optics will drive next-gen nets, Swift said.

Cisco on SDN and power
Separately, Swift downplayed the potentially disruptive shift for Cisco of software-defined networks (SDNs) using the OpenFlow open-source protocol. He said networks are moving past SDNs to "application-centric intelligent networks."

"SDN means different things to different people at different places in the net," Swift said.

Cisco wants to bring greater programmability to the network above the level of ASICs and operating systems. "We believe the higher up you go the better," he said.

Separately, he said the industry faces power consumption problems from the ASIC to the data centre that will take multiple companies to solve. Even though individual components may be more than 90 per cent power efficient, at the data centre "you still lose 25 per cent of you power and you haven't done anything yetand that's the state of the art data centre," Swift said.

"I'd love to say we have a great solution, but we are fortunate to have partners to help us with this," he said to a packed lunch audience of engineers at the first day of DesignCon.

- Rick Merritt
??EE Times

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