SANTA CLARA, Calif. – Cisco Systems is prototyping silicon photonics using 2.5-D silicon interposers, according to a senior engineering executive in a keynote at DesignCon here. The communications giant is one of a handful of companies trying to harness the technology to drive down the costs of next-generation networks.
“The convergence of optical and semiconductor ecosystems will have a huge impact for networking at 40 and 100 Gbits/second and beyond,” said Bill Swift, who leads Cisco’s transceiver and module group.
Swift showed a rough diagram (below) of a 2.5-D 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 startup Lightwire (Allentown, Penns.) in February 2010 for $271 million.
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Lightwire’s first generation product used wavelength division multiplexing to put four 25G channels over a single fibre, sources said. Along with startup 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. Startups 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.
Swift said 3-D ICs will reduce chip power and accelerate integration. The 2.5-D 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.