Steve Swanson, Corning Inc.
Misconceptions about optical fiber, coupled with the lack of information on fiber-optics standards, may be preventing network planners from using optical cable in building cabling applications.
Many optical fiber solutions have been developed for backbone applications (to 2 kilometers). But little effort has been made to standardize cost-effective fiber-optics solutions for intrabuilding runs to 300 meters, even though an industry study has revealed that runs of less than this distance represent more than 95% of combined horizontal and backbone intrabuilding cabling. As a result, much misinformation has been disseminated about the viability and cost of implementing optical fiber solutions in easily upgradable high-speed local area networks. In fact, cost-effective in-building solutions already exist, specifically for the higher data rates. However, they need to be adopted in addition to the campus backbone solutions.
The Telecommunications Industry Association (Arlington, VA) chartered the Fiber Optic LAN Section to review current technology options and show where existing standards support the use of fiber. The group is also considering standards that need to be written or revised.
The standards committee of the Fiber Optic LAN Section has looked at horizontal cabling (100 meters or less), in-building cabling (300 meters or less) and campus backbone cabling (2000 meters or less). In its work, the committee has assumed 62.5/125-micron multimode fiber with a bandwidth of at least 160 megahertz/kilometer at 850 nanometers and 500 MHz/km at the 1310-nm window.
The results of this study underscore the flexibility and upgradability that fiber brings to a premises network. At distances to 300 meters, standard 62.5/125-micron multimode fiber has the capacity to support transmission rates of 10 megabits per second for Ethernet networks all the way to the 2.5-gigabit-per-second rates of synchronous optical network and asynchronous transfer mode. It can support rates to 155 Mbits/sec in backbone distances to 2000 meters. With multimode fiber, therefore, a cabling plant can remain intact and only the electronics needs to be upgraded to support higher data rates.
Cost-effective multimode transceivers that will support data rates of more than 1 Gbit/sec for distances to 300 meters are also available. And emerging technologies, such as the vertical cavity surface-emitting laser, promise to deliver even higher data rates on 62.5/125-micron multimode fiber--at lower cost.
For network planners to take advantage of these fiber solutions, however, standards bodies must help define and validate the technologies involved. This is why the Fiber Optic LAN Section contends that all new and existing commercial optical fiber application standards should include cost-effective solutions for distances of 300 meters and less. Once network planners are aware of all available solutions, they will understand how they can use optical fiber for their entire network--not just the backbone.
For a copy of the Fiber Optic LAN Section premises fiber technology recommendations matrix, contact the TIA at (703) 907-7723.
Steve Swanson is manager of standards engineering at Corning Inc. (Corning, NY) and chairs the TIA Fiber Optic LAN Section`s standards subcommittee.
