Loring Wirbel

9/10/2008 6:56 PM EDT

Photonics developers in diverse fields meet at inaugural "Green Photonics Forum" to share power-saving strategies. Diverse researchers see the light in green applications
DENVER -- The Optoelectronics Industry Development Association took a horizontal environmental slash across several disciplines last week, holding a "Green Photonics Forum" here to give designers in opto-transceivers, solar PV cells, LEDs, and solid-state lighting a common platform to share ideas. While some attendees said they felt overwhelmed with learning so much outside their field of endeavor, many said they were surprised at the commonality of issues involving thin-film manufacturability, device power dissipation, and the competing trends of new technologies to green and "de-green" simultaneously.

A common concern of many developers was the coming crisis of the data center. Rick Dodd, vice president of product marketing at Infinera Corp., said that if long-haul backbones move to 100-Gbit/sec Dense Wave Division Multiplexing links, they will need 3.3 GW of electricity, requiring seven new medium-sized power plants - and that does not include power for metro fiber networks, IP routers in the backbones, or the cooling systems for major Internet peering centers.

Currently, the total power consumed by servers alone in data centers is 0.6 percent of the entire U.S. electricity consumption, said Dave D'Andrea, director of marketing at Lightwire. That rises to 1.2 percent of total U.S. electricity consumption when cooling and support systems are included. That's why developers of short-reach VCSELs and CMOS-based transceivers are concerned with the power dissipation of each high-speed link.
Getting Standards Bodies on Board
Tom Palkert, systems architect at Luxtera Inc., said a big difference can be made in power dissipation merely by shifting the data center from copper to fiber. A Category 6 unshielded twisted-pair 10-Gbit network can cost $28,369 in electricity bills, while a fiber 10-Gbit network costs $5,910 a year.

Palkert, who serves as chair of the OIDA's Silicon Photonics Alliance, has been reaching out to groups such as the Ethernet Low-Power 802.3az task force, and the Fibre Channel and SAS groups for low-power storage. He talked of the hurdles in reducing power for storage applications in the speech excerpt and interview in the video player.

Jack Jewell, a former Bell Labs laser researcher who founded both Vixel Corp. and Picolight Inc., told the forum why he saw VCSEL architectures as the best low-power alternative for short-reach 10-Gbit links. Jewell made a pitch for active cable, in which VCSEL transceivers are embedded directly into a fiber cable, eliminating the need for (and power dissipation) electro-optical interconnect components. In a video interview after the forum, Jewell admitted that, given the state of broadband communications, he was there as much to learn about solar PV cell development as to share information on optical tranceivers.

Efficiency gains in the PV realm
Scientists from the nearby National Renewable Energy Laboratories were on hand at the forum to discuss their own breakthroughs in concentrator-cell efficiency, and compare the milestones to those in other realms. Principal scientist Sarah Kurtz said that NREL's recent announcement of 40.8 percent efficiency for a multijunction two-terminal concentrator cell implemented in GaAs brings the industry close to the grail of cost-competitiveness with other electricity-generating methods. Concentrator architectures carry the additional advantage of using less silicon than direct PV solar panels, she added.

Dean Levi, who manages electro-optical characterization at NREL, pointed out that silicon shortages in the single-crystal world are lessening because silicon suppliers finally are ready to ramp up to perceived needs of PV startups. For many years, he said, silicon ingot suppliers were reticent at producing as many wafers as the industry claimed, having been burned during semiconductor booms. By last year, new investments and orders showed that the PV boom was real, and the shortages should be over by next year. Levi said that the global PV market should reach $150 billion by 2011, representing more than 20 GW of generated electricity.

While concentrator cells remain in front on electrical efficiency, Levi said SunPower had shown 25 percent efficiencies for single-crystal cells, and new thin-film concepts using compounds such as copper-iridium-gallium-selenide (CIGS) or cadmium-telluride, could achieve efficiencies greater than single-crystal silicon. Levi said that deposition concepts were as relevant as materials. New methods such as a spray-on printing method for CIGS, developed at NanoSolar, could achieve as many gains as new thin-film materials.