Saturday, January 5, 2008
Researchers discover a way to briefly store data acoustically to alleviate traffic bottlenecks
New Way to Help Networks Handle Ever-Heavier Data Loads
As demand for streaming video over the Web, voice over Internet protocol (VoIP) calling services and other forms of Internet-based multimedia communication skyrockets, content creators and consumers are counting on fiber-optic networks to handle these increasing loads quickly and efficiently. One way to ensure this happens is to enhance the ability of such networks, which transmit data over glass or plastic threads, to capture and retain data even for very brief intervals.
Toward that end, a team of researchers from Duke University and University of Rochester's Institute of Optics recently reported in Science that it successfully transferred encoded information from a laser beam to sound waves and back to light waves, a breakthrough that could speed development of faster optical communication networks. Swapping data between optics and acoustics allows it to be stored in pockets of acoustic vibration created when laser beams interact along a short strand of optical fiber.
The research is significant, because it addresses how memory can be created for optical pulses. "The primary thrust is investigating slow light via stimulated Brillouin scattering, where we slow down a pulse as it propagates through an optical fiber," says study co-author Daniel Gauthier, chairman of Duke's department of physics. Brillouin scattering occurs when light traveling through a medium, such as glass, changes its path as it encounters varying densities.
The main goal of the research is to pave the way for better fiber-optic communication systems, which today consist of fiber placed underground and linked by routers. The typical way to send data over an optical network is to break it up into chunks called packets. When a packet comes into a router, its address information is read. The problem with routers is that they each contain a single switch that can only process one packet at a time. As a result, some packets are dropped unless others coming in are buffered (saved) or can wait until it is their turn to be routed. "If you drop the packet, you reduce the throughput of the entire network," Gauthier says. "If you buffer, then the packets are processed one after the other."
As greater demands are placed on telecommunication infrastructures, "it's important to start to investigate parallel technologies," he adds.
Gauthier and his colleagues discovered that when two laser beams of slightly different frequencies are pointed at one another along a piece of glass fiber, they create acoustic vibrations called phonons. When co-author Zhaoming Zhu, Gauthier's postdoctoral research associate, encoded information onto one of these beams, the data could be imprinted on these newly created phonons and retained for 12 billionths of a second, long enough to be transferred back to light again by shining a third laser through the fiber.
"When thinking about how to store light in optical fibers," Zhu says, "we realized that we can convert optical information to acoustic vibration, something that hasn't been done before."
The researchers are seeking ways to create longer storage times and reduce the peak power of the laser beam needed for retaining and reading out the information, a process that will take years before a commercial version of the technology is available.
"There is still a great need for developing new strategies for optimizing the flow of information over the Internet," says Robert Boyd, a professor of optics and physics at the Institute of Optics and a research co-author. "If two data packets arrive at a switch at the same time, you need to store one until the other packet clears the switch, maybe 100 nanoseconds later. Our technique is aimed at … building buffers for high-speed telecommunications."
During the first phase of the project—which is part of the Defense Advanced Research Projects Agency's (DARPA) Defense Sciences Office slow-light program—Zhu says he learned that pulses could be stored and read out at a later time. The second phase was the actual experiment in which data pulses were stored (as acoustic waves in an optical fiber) and retrieved after a certain period of time.
"We really want to demonstrate that methods for storing optical information are much broader than people thought," Gauthier says. "In the current telecommunication systems, you turn the optical signal into an electronic signal and store it in RAM. The optical data pulses are then regenerated by using the electrical signals to turn on and off an auxiliary laser source. But this process generates heat. The faster this is done, the more heat is generated."
For this to work in the real world, the scientists say the communication fibers must be made of a material that provides an acoustic time frame long enough to allow the information to move from optical to sound, then return to optical. One option, Gauthier says, is to work with a new type of glass made from a chalcogenide, which has good semiconductor properties and contains one or more elements from the periodic table's chalcogenide group, also known as the "oxygen family," which includes oxygen, sulfur, selenium and tellurium.
Another option that researchers are exploring is to run the laser beams through a hollow optical fiber filled with gas (such as xenon), which would allow them to use a less powerful laser to induce longer lasting sound waves in the gas. This could potentially create a sound wave 50 times longer and allow the lasers used to be 100 times less powerful—and less energy intensive—thereby delivering more data more quickly at a lower cost.
New Video VoIP Software, Webcams End That Pixelated Feeling
Skype and Logitech team up to deliver video voice over Internet protocol calls that look more like TV than home videos
Thanks to the rapid-fire growth of broadband network connectivity, video voice over Internet protocol (VoIP) services now give callers around the world the ability to gab away for no more than the cost of their monthly Internet service provider fee. Until now, though, the video capabilities have been little more than a novelty that tempts callers with grainy images of their friends and family that lack the ability to capture their movement with any fluidity.
But that could change as early as next month when Luxembourg–based Skype, a division of online auctioneer eBay, is set to unveil the latest version of its software, which is tuned to work with a new lineup of "high-quality video" Web cameras from Fremont, Calif.–based Logitech. The companies gave a preview Tuesday of what's to come at a New York City press conference, where they demonstrated their software and hardware working together to produce video VoIP that looks more like watching TV than grainy home movies.
This is no small feat, as the laundry list of requirements indicates. What do you need to take advantage of this latest offering? Skype 3.6 (coming in early to mid November), any of three new Logitech Web cameras introduced Tuesday, the latest version of Logitech's Web camera drivers, a bandwidth connection of at least 380 Kbps (kilobits per second) and a PC with at least one gigabyte of RAM and a dual-core, 2.0 GHz (gigahertz) or faster processor running Windows XP or Vista. The result will be a sharp video image resolution of 640 by 480 pixels at up to 30 fps (frames per second), up from Skype's previous capacity of 320 by 240–pixel resolution at no more than 15 fps.
The goal, the companies say, is to alleviate some of the frustrations that video VoIP users must contend with, in particular the choppy, pixilated images of loved ones that freeze and jump during VoIP conversations. The upgrades in software and camera equipment are designed to "make people feel like they're together during a conversation," even if they are separated by hundreds of miles, Don Albert, vice president and general manager of Skype North America said at the press conference.
Added Gina Clark, vice president and general manager of Logitech's Internet Communications business unit: "Our goal is to make lifelike video calls.''
Have an Apple? Sorry. You'll have to stay on the sidelines—at least for awhile. Albert said there was currently no plan to release a Mac version of Skype 3.6, but Logitech's Clark said she would be interested in exploring the new cameras' performance on Macs, even though most Macs now come with embedded Web cameras.
All three of Logitech's new Web cameras offer a glass lens made by Oberkochen, Germany–based optical lens maker Carl Zeiss. (Most Web cameras come with plastic lenses, but more expensive glass lenses produce higher quality images.) The cameras also include an autofocus feature that resolves images in less than three seconds and can handle close-ups up to about four inches (10 centimeters) from the lens. The price tag for the new Web cameras: $100 and up.
Skype, which earlier this week introduced a 3G Internet phone with built-in software, says that 25 percent of its 246 million users worldwide use their VoIP technology to make video calls to other Skype users. Although Skype has offered VoIP since 2003, it has offered video calls for only about two years. Interest in video VoIP is expected to grow, but it will only go as far as broadband connectivity can permeate. Logitech estimates that half of U.S. households currently have access to broadband.
Posted by SANJIDA AFROJ at 9:34 PM