More on theoretical limits. A physics lesson for a certain guru. - JGH
Wednesday June 27 8:43 PM ET
Lucent Finds Theoretical Outer-Limits of Fiber
MURRAY HILL, N.J. (Reuters) - Lucent Technologies Inc. (NYSE:LU - news) said on Thursday its Bell Labs scientists found that a single strand of optical fiber could transmit 10-times more information than previously thought, which means the potential power of such networks has yet to be realized.
The Bell Labs team, whose scientific results appear in Thursday's issue of the British journal Nature, found that it is theoretically possible to send about 100 terabits of information, or roughly 20 billion one-page e-mails, simultaneously per strand of fiber.
Note: This is approximately ten to twenty times Ciena's currently commercial DWDM systems capability at 10G bit rate. 40G electronics will expand the envelope even further when these electronic chips become cost-effective. 80G electronics are still in the lab research phase. The article does not address the distance factor which is also critical to throughput, as the signal degrades over distance. It should therefore be apparent that everyone will not get his own wavelength. There are physical limits. - JGH
Current commercial optical systems can transmit just under two terabits of information per second and laboratory experiments have demonstrated transmission rates of 10 terabits per second.
``This paper highlights the fundamental understanding of the ultimate capacity of fiber,'' said Alastair Glass, chief technical officer of Lucent's Optical Networking Group. ``It says that we are still a long way from the fundamental limits in current commercial systems, and it's still uncertain when optical systems will be able to approach the theoretical limits.''
Network builders and telephone companies spent about $90 million over the last four years laying fiber-optic networks in the United States, where there's now 39 million miles of glass fiber.
Analysts estimated that less than 5 percent of that fiber is ``lit,'' or has the electronics, amplifiers, and software needed to transmit information. CS First Boston estimated less than 1 percent of the fiber in the ground is used.
Those estimates have sparked much industry debate about a broadband glut and cast a pall over the U.S. telecommunications market, pushing down stock prices and spooking investors.
It had been difficult to theoretically calculate how much information can be transmitted over a glass fiber because the physical properties of glass make light transmitted over fiber susceptible to scrambling, Lucent said.
In doing their research, the Bell Labs looked at telecommunication systems that use wavelength division multiplexing -- a technique that expands the capacity of a strand of fiber -- and estimated how much information can be conveyed from a transmitter to a receiver.
If a signal is sent with too little power, it will be overcome by the noise in the system. However, sending a signal that is too powerful will interfere with other signals.
With wavelengths and values typically used in communication networks, the scientists determined that it is theoretically possible to send 100 terabits of data per second without excessive noise or interference, Lucent said.
Bell Labs is the world's largest research and development organization dedicated to communications with 30,000 employees in 30 countries. |
