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Photonic chips could be the basis of detection systems sensitive enough to read the date on a dime from a mile away.

Light Fantastic

The telecommunications networks that now stretch around the world transmit information optically, carrying Internet, television, and telephone signals in the form of pulses of light. It’s more efficient to move data that way than as electronic signals, and photonics promises to revolutionize not only telecommunications, but entertainment, medicine, computing and a multitude of other applications.

Although most of the long-distance networks that span the world are optical networks, photonic technology isn’t yet so ubiquitous in smaller scale connections. Data that’s traveled thousands of miles over fiber optic cables must still be converted to electrical signals before it can be detected and processed by switches, routers and other devices that handle data on its way to an end user. That’s a slow, energy-intensive process, and one that researchers are targeting in their efforts to replace sluggish electrical connections with blazing fast photonic links.

Researchers also are looking to use optical connections within computers, and, ultimately, on an even smaller scale: on all-optical chips. UC Santa Barbara researchers are building on the university’s strengths in materials science, fabrication and engineering to develop photonic components and devices for a new generation of high-performance, energy-efficient communications and information processing systems.

Two research efforts recently launched at UCSB aim to advance photonic technology for a multitude of potential applications, from remote sensing to communications to terabit Ethernet technologies for high performance Internet and networking.

Larry Coldren

“These coherent PICs will provide a huge increase in the amount of information that can be transmitted from or received by a single chip as well as a tremendous reduction in the size, weight and power required by the chips.”

Larry Coldren

A revolution on a chip

A new UCSB-led consortium, Photonic Integration for Coherent Optics (PICO), will develop photonic chips for communications and sensing applications. Acting Dean of Engineering Larry Coldren, who’s heading up the PICO group, says these chips could handle massive amounts of data—making it possible to download dozens of feature films in a second—and be the basis of detection systems sensitive enough to read the date on a dime from a mile away.

Following a national competition, the multi-university-industry consortium was one of four chosen for funding—a little more than $2 million a year—from the U.S. Defense Advanced Research Program Agency (DARPA). PICO will receive about the same amount from industry sources.

The consortium includes researchers from the Massachusetts Institute of Technology, the California Institute of Technology, the University of Virginia, Lehigh University, and 17 industry partners including Hewlett-Packard, Intel and Rockwell-Collins. The other UCSB participants are professors John Bowers and Mark Rodwell and research engineer Leif Johansson.

Research at PICO will draw on UCSB’s world-leading expertise in designing and fabricating photonic integrated circuits (PICs). These devices, which pack a great many components onto a single tiny chip, are intended to be the basis of powerful new optical communications and computing systems. PICO researchers aim to develop a new generation of PICs that operate on both the amplitude and phase of lightwaves. “These coherent PICs will provide a huge increase in the amount of information that can be transmitted from or received by a single chip, as well as a tremendous reduction in the size, weight and power required by the chips,” Coldren says.

The PICs to be developed at PICO will draw on both silicon technology, which would enable them to be fabricated using the CMOS processes that currently dominant chip manufacturing, and on monolithic indium phosphide technology, Coldren (pictured below) says.

Among the potential applications that PICO researchers have in mind for the chips is in LIDAR detection systems that use light generated by lasers to map terrestrial objects from the air, and in communications systems using either conventional fibers or narrowly focused beams of light to deliver information to a specific target such as a pilot, minimizing the possibility that the signals will reach some unintended recipient.

Future Internet: 1000x faster

Imagine if all the data traversing the world right now—the television broadcasts traveling over long-distance networks to living rooms around the country, the databases and files being exchanged over office networks and all the information moving within computers and other hardware—could be sent through a single fiber the width of a human hair. That’s the vision driving a new research collaboration established at UCSB, with support from industry partners like Google, Intel and Verizon.

“We’re going to need much faster networking to handle the explosion in Internet traffic and support new large-scale applications like cloud computing,” says Daniel Blumenthal (pictured right), professor of Electrical and Computer Engineering at UCSB. He directs the Terabit Optical Ethernet Center (TOEC), which is part of UCSB’s Institute for Energy Efficiency.

Blumenthal

“We’re going to need much faster networking to handle the explosion in Internet traffic and support new large-scale applications like cloud computing.”

Dan Blumenthal

Researchers with TOEC aim to develop the technology necessary for a new generation of Ethernet—the de facto standard for data transmission both on a small scale and across global networks. It will be a thousand times faster and much more energy-efficient than today’s most advanced networks. Blumenthal and colleagues at TOEC are aiming for 1 terabit Ethernet over optical fiber—1 trillion bits per second—by 2015, with the ultimate goal of enabling 100 Terabit Ethernet by 2020.

It won’t be easy. Ethernet is constantly evolving, but soon—perhaps in as little as five years, according to some estimates—it won’t be able to keep up with the surge in Internet traffic as private and public enterprises move increasingly massive quantities of data, and consumers stream video, share high definition photos and explore and interact within sophisticated online environments. Millions of people will soon be consuming billions of bits per second in their living rooms—simultaneously.

Current Ethernet technologies can’t be pushed much past 100 gigabits per second—the speed that’s beginning to be implemented now—mainly because of the amount of power needed to run and cool the required systems, Blumenthal says. New generations of Ethernet need to be much more energy-efficient and cost-effective in order to overcome the power problem.

“Our goal,” Blumenthal says, “is to make energy-saving technologies that will allow applications and the underlying networks to continue to scale as needed. You could think of it as greening future networks, and the systems that rely on those networks.”

That, Blumenthal says, will require fundamental improvements in underlying technologies—advances that will be underpinned by photonic technology developed at UCSB. Research at TOEC will draw on UCSB’s world-leading expertise in materials, advanced electronics, photonic integrated circuit technology, silicon photonics and high-speed integrated optical and electronic circuits, and in bridging these new technologies with real networking systems. It will include ongoing work on a DARPA-funded project aimed at eliminating the requirement for optical signals to be converted to electrical signals before they’re redirected or otherwise processed. As part of that project, Blumenthal and colleagues at UCSB have developed an optical router—the monolithic tunable optical router (MOTOR)—on a single chip. It’s an important step toward replacing bulky, energy-hungry router hardware with smaller, more efficient all-optical routers. MOTOR is one of the largest and most complex PICs ever created and it’s helped secure UCSB’s standing as a world leader in the field, says Bowers, who is also part of TEOC and focuses on developing integrated circuit technology on silicon substrates—an approach that would enable chips to be fabricated using CMOS processes.

All told, Blumenthal says, TOEC’s vision will require “dramatic breakthroughs across multiple disciplines, not only in the core Ethernet technologies but in Ethernet-based networking and in the engineering and measurement systems used to develop and test these new technologies.”

It’s a big ask, but the payoff could be huge. Not only will terabit Ethernet soon be needed to satisfy the demands created by the way we use networks now, but Internet pioneer Dave Farber, a professor at Carnegie Mellon University, says high-performance, high-speed Ethernet will open up opportunities we couldn’t dream of today: “You build it and they will come,” he says.

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UCSB’s photonics researchers have claimed many firsts, including the world’s first eight-channel monolithic tunable optical router (MOTOR) that operates error-free at 40 Gbits/per port on a single InP/InGaAs chip. It was developed in the labs of professors Coldren and Blumenthal.

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