Lucent develops multimode system for 10-Gbit speeds

While the world of cabling and communications is just getting its collective hands around 1000-megabit-per-second Gigabit Ethernet, the drivers of technological change are thinking about speeds 10 times as fast. That desire for faster speeds was evident at the recent BICSI (Tampa, FL) conference in Reno, NV, when Lucent Technologies (Murray Hill, NJ) introduced the newest addition to the Systimax Structured Connectivity Solutions line--LazrSPEED.

Nov 1st, 1999

Patrick McLaughlin

While the world of cabling and communications is just getting its collective hands around 1000-megabit-per-second Gigabit Ethernet, the drivers of technological change are thinking about speeds 10 times as fast. That desire for faster speeds was evident at the recent BICSI (Tampa, FL) conference in Reno, NV, when Lucent Technologies (Murray Hill, NJ) introduced the newest addition to the Systimax Structured Connectivity Solutions line--LazrSPEED.

Designed to alleviate backbone congestion in local area networks (LANs), LazrSPEED provides what Lucent calls "a cost-effective road map from today`s 10-Mbit/sec technology to the 10-gigabit-per-second backbones of the future." It does so by providing the ability to support light- emitting-diode-based 10-Mbit applications through vertical-cavity surface-emitting laser-based 10-Gbit applications on the same fiber.

The key element in the system is a new 50-micron fiber that Lucent says outperforms conventional 50-micron fiber. According to the company, the new fiber is sufficiently robust to support 10-Gbit speeds to 300 meters. The performance is attributed to the attention paid to the fiber`s light-propagation properties. The fiber characteristics for conventional multimode fiber cause light pulses to arrive at the receiver at different times, thereby spreading signal energy out over many bit periods and causing interference and errors. Characteristics of the LazrSPEED fiber keep the signal concentrated in a single wave that does not cause interference between bits, the company reports.

The LazrSPEED system also includes the LC fiber-optic connector and a new line of enterprise-distribution apparatus.

Inadequate installed base?

Part of Lucent`s rationale for developing the new system is that the current installed base of multimode fiber, or at least most of it, cannot adequately support 10-Gbit transmission. "The installed base of multimode fiber can only support 10-Gbit/sec speeds for a few tens of meters unless complex optoelectronic techniques such as multichannel wavelength multiplexing are used in the equipment," the company said in a Bell Labs report that accompanied the system`s announcement. "Such short distances may be useful for equipment interconnections within a computer room, but fall far short of what is needed to serve building backbones."

The LazrSPEED system, Lucent contends, provides the performance necessary to support single-channel transmission--considered the simplest optoelectronic technique used in all fiber LAN solutions to date.

While it is apparent that the system can support high speeds, it is also flexible, reliable, and cost-effective, according to John George, a fiber-offer development manager with Bell Labs. "The system allows users to use one fiber path for 10-Mbit through 10-Gbit," he says. "There`s no need for hybrid cable or singlemode. The fiber`s capabilities allow for gradual migration and don`t mandate a forklift-type upgrade. Upgrades can be accomplished seamlessly."

In terms of reliability, George points out the 20-year warranty and guaranteed application support to 300 meters at 850 nanometers. "For 1-Gigabit Ethernet, it guarantees support to 600 meters at 850-nm, with four LC or two SC or ST connections."

Cost-effectiveness comes in when you consider that the system is optimized to support 10 Gbits at 850 nm. "That`s more cost-effective than a 1300-nm approach," George says. "A 1300-nm system has to be built with much tighter tolerances because it`s for both multimode and singlemode."

He says Lucent conducted research into the relative cost projections for upgrading a 1-Gbit/sec LAN backbone to a 10-Gbit/sec backbone, using four approaches:

•Using the installed base of multimode fiber, which also necessitates the use of wavelength-division multiplexing electronics

•Using singlemode fiber for both 1- and 10-Gbit/sec applications

•Upgrading an existing multimode infrastructure to singlemode for 10-Gbit/sec applications

•Using the LazrSPEED multimode-fiber cabling system.

While costs were estimated for the research and Lucent stresses that exact costs will differ in each case depending on users` specific configurations and other costs, the company`s estimates show the three alternatives to LazrSPEED are between 30% and 50% more expensive than the new system.

"LazrSPEED is not just a multimode fiber," says Luc Adriaenssens, Lucent`s director of Systimax research and development. "It`s a complete system that has been in development for approximately 18 months."

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