More solutions now standards-compliant

The revised standard, ANSI/TIA/EIA-568B.3, opens the door to an increasingly fiber future.

By Herb Congdon and Bob Jensen

Maybe you've already used small-form-factor (SFF) connectors to reduce the costs of your horizontal fiber-cabling system. Maybe you've installed 50-micron multimode fiber in your network. Or maybe you've been waiting on a standards consensus before making the move away from copper.

If that's the case, full speed ahead! After two years of debate and discussion, the Telecommunication Industry Assoc iation's TR-42 Committee has validated the use of these technologies by including them in the newly revised ANSI/TIA/EIA-568B.3, the section that covers optical-fiber technology. Revisions to the two remaining sections, 568-B.1 (containing general requirements) and 568-B.2 (on balanced copper cabling) will follow soon.

The Commercial Building Telecom munications Cabl ing Standard is the bible for premises system design in an industry where stand ards compliance provides network de signers with the security that they are following a path of proven performance. For new technologies like SFF connectors to enjoy widespread acceptance before being ratified shows how strong the desire has been to find technologies that enable the cost-effective deployment of fiber in the horizontal. For more established products, like 50-micron multimode fiber, the inclusion in the standard shows how the industry is moving beyond the view of multimode fiber that was established with the Fiber Distributed Data Interface (FDDI) standard a decade ago.

One of the most significant changes to TIA/EIA-568 is that for the first time, the standard defines connector choice through the performance requirements (optical, mechanical, and environmental) that an optical-fiber connector or patch-cord assembly used in the premises environment must meet, rather than specifying connector designs.

The two main requirements are that a connector product must have a Fiber Optic Connector Intermateability Stan dard (FOCIS) document (TIA/EIA-604-XX) to ensure that products made by different manufacturers will mate with good results. Second, the connectors must meet the mechanical and environmental performance requirements set forth in Annex A of TIA-568B.3.

The basic minimum requirements for an optical connector are maximum loss of 0.75 dB for multimode or singlemode fibers and a minimum return loss of 20 dB for multimode and 26 dB for singlemode fiber.

By focusing on performance, the TR-42 committee gives network designers more flexibility in their choice of connector. Rather than excluding specific designs, network managers can install SFF connectors or deploy the more traditional SC-duplex or ST-compatible designs.

For IT decision-makers, this flexibility can help them make a more balanced decision about whether to run fiber in the horizontal cabling portions of their network because they can now save money and comply with the standard. In networks where they've already been deployed, SFF connectors have helped reduce installed first costs in several ways. First, SFF connectors generally cost less and are easier to install than traditional connectors (thus saving labor costs); second, their small footprint allows LAN manufacturers to achieve port densities equal to copper products, leading to substantial cost reductions.

Including 50-micron optical fiber as a standards-compliant medium may seem extraneous. After all, the 62.5-micron fiber widely used today in premises networks meets the vast majority of network requirements, especially in the horizontal. However, providing network designers with more choice gives them the flexibility to make the right decision for their network and not force them to move in step with the "majority." While 50-micron fiber has not been as widely used in the U.S. market as 62.5-micron fiber, this fiber design was actually introduced a decade earlier and has demonstrated its reliability and performance in European networks for decades.

The decision to include 50-micron multimode fiber was likely driven by the increasing use of vertical-cavity surface-emitting lasers (VCSELs). These low- cost lasers al low users to extend their multimode net works to gigabit speeds while operating in the 850-nm window. While both fiber types can be used with VCSELs and run Gigabit Ethernet and higher-speed protocols, standard 50- micron will be able to do so over longer distances at the 850-nm window. This is because, at that wavelength, 50-micron fiber has higher-bandwidth characteristics; it provides a minimum bandwidth of 500 MHz-km at 850 nm, compared to the 160 MHz-km afforded by standard 62.5/125 micron. At 1,300 nm, 62.5-micron and 50-micron fibers provide similar performance.

The revised standard includes all specifications for fiber performance, including physical, mechanical, optical, and environmental.

Looking at the changes to come in the other sections of the standard, perhaps the most significant is that Annex A of the pending TIA-568B.1 will elevate the status of centralized optical-fiber cabling from a technical-service bulletin (TSB-72) to an normative annex.

First introduced in 1997, centralized cabling was the first premises-cabling system design that complies with the Commercial Building Telecommunica tions Cabling Standard and allows network designers to capitalize on the performance benefits offered by optical-fiber cabling. By leveraging the high bandwidth and low attenuation of multimode fiber, network designers are able to centralize LAN electronics in one communications room within a building. Centralized networking with optical fiber offers users the ability to contain, and even reduce, their operating costs, while simultaneously adding flexibility, control, and accessibility to their networks.

The revisions to the Commercial Building Telecommunications Cabling Standard reflect the trends that have already been established in the marketplace. Network designers continue to seek out ways to increase their network's bandwidth while at the same time finding ways to lower costs. The changes contained in the revised standard support both those goals with a host of products that have proven their performance and value in the installations of com panies worldwide.

ANSI/TIA/EIA- 568B.3 is available from Global Engineering Documents by calling (800) 854-7179 (United States and Canada), outside the United States at (303) 397-7956, or from the company's Website at http://global.ihs.com.

Bob Jensen, RCDD, works for 3M Telecom Systems Div. as the technical-services team leader for the Volition Network Solutions. As an active participant in TIA TR-42 and its subcommittees and working groups, Jensen chairs subcommittee TR-42.2, Residential Cabling, chairs the TR-42.3 Pathways Fill Task Group and Spaces, is editor of the Customer-owned OSP Standard, and is secretary for TR-42.