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Is silicon photonics an industry game-changer? Embracing manufacturing and business models common to the chip industry promise to shake up the optical component industry.
Teraxion is developing a coherent receiver for CFP2 . “We believe silicon photonics is the material of choice to fulfil CFP2 requirements while allowing even smaller size reduction for future modules such as the CFP4,” said Martin Guy, Teraxion’s vp of product management and technology. Start-up Skorpios Technologies is using hybrid integration that combines III-V and silicon at the wafer scale. “We have projects spanning everything from access all the way to long haul, and covering some datacom as well,” said Rob Stone, vp of marketing and program management at Skorpios. Perhaps the biggest impact silicon photonics will be on the supply chain. Cisco’s decision to make its own 100Gig transceivers impacts module makers and undermines the concept of MSAs. Silicon photonics also moves optical component manufacturing to an ASIC model. Companies could design an optical chip and go to a foundry for its manufacture, package it and place it on their cards, skipping module makers altogether. Yet the ASIC model can also benefit module makers. IBM, for example, is using its optical engine for its systems and server designs; it is less interested in data centre interconnect up to 2km. But IBM is open to its technology being used by transceiver providers. “There are companies with the potential to offer a design service or foundry service to others that would like to access this technology,” said Cisco’s Carter. “Five years ago there wasn’t such an ecosystem but it is developing very fast.” Roy Rubenstein Editor of the online publication, www.Gazettabyte.com
Intel views silicon photonics as a way to boost microprocessor sales by enabling new server architectures. Intel is part of Facebook’s Open Compute Project where optics is used for a disaggregated rack server design that separates storage, computing and networking. “When I upgrade the microprocessors on the motherboard, I don’t have to throw away the NICs and disk drives,” said Victor Krutul, Intel’s director of marketing, silicon photonics operation. IBMhas announced what it claims is the highest density optical engine, built using 90nm CMOS. “Silicon photonics does compete in terms of cost with VCSELs, if all elements of the cost are taken care of: bill of materials, packaging and testing,” said Yurii Vlasov, manager of the silicon nanophotonics department at IBM Research. But not everyone believes silicon photonics will replace VCSELs. “The VCSEL by nature is an incredibly efficient, low cost solution,” said Zirngibl. And Valery Tolstikhin, founder and former CTO of indium phosphide specialist, OneChip Photonics, and now an independent consultant, questions the merits of silicon photonics for transceiver designs. “There are places where silicon photonics will definitely win, such as chip- to-chip optical interconnects, and there are places where there is still a question mark, like fiber-optics interconnects,” he said. At the other end of the optical performance spectrum, silicon photonics is being use for long- distance transmission. The technology could shrink coherent designs to fit within the CFP2, albeit at the expense of reach. A CFP2 coherent module has extremely challenging cost, size and power requirements.
tricky to couple light in and out of a chip. Silicon photonics’ huge advantage, however, is its ability to piggyback on the semiconductor industry’s vast investment in CMOS. CMOS processes use 8- and 12-inch wafers to deliver high yielding chips. “If you match any component with that type of process, you have instant high volume and instant scalability,” said Martin Zirngibl, domain leader, enabling physical technologies at Alcatel-Lucent’s Bell Labs. First silicon photonics designs span optical interconnect for the data centre to 100Gbit/s long- distance transmission. Customers care little about the underlying technology but do care about cost, power, interface density and optical performance. One data centre issue is the need for longer reach links. VCSEL technology is an established solution but at 100Gbit/s its reach is 100m only. For greater distances, a second technology is required. Data centre operators would like one technology that spans the data centre yet is cost competitive with VCSELs. “Silicon photonics lends itself to that,” said Adam Carter, general manager and senior director of the transceiver modules group at Cisco.Cisco’sfirstsiliconphotonics product is the CPAK, a 100Gbit/s pluggable module, slightly smaller than the CFP2 MSA. Luxtera, whose silicon photonics technology is used for active optical cables, and Mellanox’s Kotura, are each developing a 100Gbit/s QSFP to increase reach and face plate density. Two companies readying first products are Intel and IBM. Intel has detailed a 100Gbit/s transceiver and is working with Corning on a 1.6Tbit/s connector.
By Roy Rubenstein T he last 18 months has seen noteworthy developments in silicon photonics. System vendors Cisco Systems acquired silicon photonics start- up, LightWire, for $272M while Mellanox Technologies announced its intention to acquire Kotura for $82M million. System vendors are also using embedded optics to differentiate their hardware. Arista Networks’ 7500E switch has a line card with board-mounted optics rather than pluggable transceivers to increase 100Gbit/s port density. And Compass-EOS has developed chip-mounted optics using 168 lasers and 168 detectors for its IP core router that removes the need for a switch fabric and mid-plane to interconnect the router cards. Both companies use VCSELs, an established laser technology that silicon photonics competes with. Yet the system designs highlight how moving optics closer to the silicon enables system innovation. Silicon photonics also competes with indium phosphide, the bedrock of the optical component industry. At first glance, silicon is an inauspicious material for optics. Silicon does not lase, requiring III-V material or an external laser for a circuit’s light source. Silicon’s small waveguides also make it
14 | Optical Connections 2013 | www.opticalconnectionsnews.com |
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