Publications
The Future of Optical Networking
For those of us who used to dial up to get online, the day broadband arrived will always be remembered fondly. Widely available high-speed connections not only made surfing the Web a faster, more pleasant experience, it ushered in a whole new era of Web content and applications. Suddenly you could have videoconferencing, voice over internet protocol (VOIP), music file-sharing, and video blogs.
So imagine what the Web would be like with connections that are 10,000 times faster than those we have today.
Connie Chang-Hasnain, UC Berkeley EECS Professor
"It will totally transform our society," says Connie Chang-Hasnain, the John R. Whinnery Chair Professor of EECS professor at UC Berkeley. "Suddenly everybody is a publisher and everybody can receive movies all the time. Three-dimensional video conferencing could totally transform many ways we do business, medicine, and education."
What will make such things possible is an optical network that is radically different from the one we have today.
"One fiber is enough to carry the entire world's Internet traffic," says UC Berkeley EECS Professor Ming Wu
Telecommunications information is carried from point to point over optical fibers, which have a very high capacity. "One fiber is enough to carry the entire world's Internet traffic," explains Ming Wu, an EECS professor at UC Berkeley. "However, the network traffic is very diverse. Many different kinds of data are being transmitted'some voice, some text'and each of them is going to a different destination," he says.
"The Internet was designed nearly four decades ago to support any applications on any physical layer platforms," says S. J. Ben Yoo, an ECE Professor and CITRIS Campus Director at UC Davis. "The Internet traffic continues to grow explosively today. While the modern multi-wavelength optical networking can now transport such traffic, it remains an extremely challenging task to route and switch such an immense amount of traffic to support demanding new Internet applications," he says.
Routing that data creates bottlenecks, because it must be converted from light to electricity and back to light before it can be sent to the next point along the network. It is a bit like having to change planes several times to get to your destination. Chang-Hasnain, Wu and Yoo are three CITRIS researchers who are developing technology that will eliminate those bottlenecks.
"We need a smarter optical network," says Wu. To that end, he is developing reconfigurable, or tunable, optical Micro Electronic Mechanical Systems (MEMS). Data passing through the network in the form of light would be organized by type and destination into different colors along the spectrum. It is a rough analogy, but think: red for "traffic" going to New York blue for Chicago green for Los Angeles. The MEMS, known as a wavelength selective switch, would detect the color, and a tiny movable mirror on the device would steer it accordingly.
Currently, changes to the optical network'such as adding a node or redirecting "traffic" to accommodate heavy bandwidth use or avoid a failed node'must be made manually. "These new tunable devices will allow the entire process to be controlled electronically or even spontaneously. When a node senses more traffic is coming this way, it will allocate more bandwidth to that channel," says Wu.
Other benefits will include networks automatically sensing the presence of new nodes'no need to log on, as you will be automatically connected'and instant access to larger bandwidth whenever you need it.
"Much of our research is focused on how to shrink the size of those smart functions and implement it on a piece of silicon," says Wu.
Prof. Yoo has recently demonstrated a new type of all-optical router that can switch data at a fraction of a "nano" second, or a billionth of a second. "Today's routers store packets, segment them into cells, switch the cells, and reassemble them into packets again. Our new optical router can pipeline and switch optical packets without storing them simply by changing the lanes or colors of the packets," says Yoo. The resulting optical router has been shown to scale to 42 Petabit per second capacity, or millions of times the switching capacity of today's large routers found in typical buildings. However, when such routers try to scale even larger, there are problems.
"Today's highest-capacity (46 terabit per second) router sold today consumes 1.25 MegaWatts of power, weighs 56 tons, and occupies a footprint of a tennis court. The fact that our optical router technologies are being integrated on a semiconductor chip scales this down to about 100 Watts of power, a half-pound weight, and the size of a lightbulb, while providing the switching capacity of 46 times the entire traffic in the United States today. This technology will completely change the way we run our data centers, healthcare centers, and entertainment businesses. It will completely transform the Internet," says Yoo.
Chang-Hasnain hopes to speed up the optical network ironically by slowing it down. "Traditionally an optical signal propagates at the speed of light. It can't be slowed down. We're looking into a method of slowing it down significantly," she says.
Just as memory buffers allow you to watch a video online without having to download it first, or a roundabout enables cars to pass through an intersection without stopping, Chang-Hasnain's semiconductor optoelectronics would bend light as it passed through routers so that it could sorted without having to be converted to electricity and back into light again.
"We actually have made huge progress in demonstrating some of these concepts already," she says. Most recently, her team built a device that delays a picosecond pulse by 2.5 times its bandwidth at room temperature.
Chang-Hasnain is also working on creating nanowire lasers to replace semiconductor lasers. By reducing the volume of light, nanowire lasers would decrease the power needed to move it through the optical network, and the time it takes to do so.
S. J. Ben Yoo, UC Davis CITRIS Director
In January, the Defense Advanced Research Projects Agency (DARPA) awarded researchers at UC Davis and MIT a grant for $9.5 million over three and a half years to fund work on new high-speed devices for optical networking. Yoo's research is aimed at designing and building thumbnail-sized chips that can encode data at rates 10,000 times faster than current ones. "This brings an exciting opportunity for us to integrate functional optical signal processing units onto a single piece of semiconductor chip. Ultrawide-band (100 THz) signal processors, synthesizers, and arbitrary waveform generation for a next generation optical networking can be enabled by using this optical chip."
"When we first started back in 2001, you could count maybe a handful of people, mostly physicists, who were working in this field," says Chang-Hasnain. "Last year, we co-chaired with the Optical Society of America (OSA) the first slow and fast light conference, we anticipated maybe 50 people. It sold out, about 120 seats, and we had to cut registration one day before it closed."
Clearly, it is an exciting time in an exciting field, in which results are expected sooner than later.
"In about five years, our network will look very different from today's network'a lot smarter and a lot more flexible," says Wu<!-- InstanceEndEditable -->