Fiber Standards Enable Low-cost, High-speed Optical Networks

Welcome to a series of monthly articles focusing on “Premises Cabling Standards and Technology Updates” by Tony Beam, director of global systems marketing for AMP NETCONNECT. Beam has more than 15 years’ experience in the premises cabling industry and has been a member of TIA for over 12 years, actively covering issues surrounding VDV. This series of articles will deal with the latest developments with premises cabling standards plus technology trends in the VDV industry. The intent is to keep you informed to best serve your customer. We welcome your feedback and suggestions for future articles. For many years, installers, end users, consultants, and contractors have had to carefully balance the benefits of new technology and products with the accepted practices and standards of the industry. The trade-offs are usually significant––install cutting-edge technologies today and risk being locked into a proprietary (sole-source) solution in the future, or insist on standards-based solutions even though more advanced technologies are available. Fortunately, with respect to optical fiber networks, standards have been issued that support the new technologies needed for today’s networks. While standards will always lag behind technical innovation due to the administrative process, recent revisions to industry standards have now “caught up” and allow end users to enjoy the best of all worlds––standards-based, cost-effective, and technically advanced infrastructure. The TIA is presently in the balloting process to revise the TIA/EIA-568-A Standard (Commercial Building Telecommunications Cabling Standard). The revised standard will be approved and published as three separate documents: B.1 covering the system level requirements, and the B.2 covering the component specifications for copper, and B.3 covering the fiber optic cabling components. While the system and copper standards are still in the ballot process, the TIA/EIA-568-B.3 Standard (Optical Fiber Cabling Component Standard) was approved for publication in February 2000. There are three primary revisions to the standard––the recognition of 50/125-micron multimode optical fiber as an allowable medium, the allowance of small form factor connectors (such as the MT-RJ optical fiber connector), and the elevation of centralized cabling from a Technical Service Bulletin (TSB) to inclusion in the standard. ANSI/TIA/EIA-568-A (Commercial Building Telecommunications Cabling Standard) listed only 62.5/125-micron multimode fiber as allowable in the horizontal. During the development of the Gigabit Ethernet Standard (IEEE 802.3z), it became apparent that the standard 62.5/125-micron fiber was limited in the lengths it could support at these high-data rates using laser sources, particularly 850 nm VCSELs. Accordingly, the 62.5/125-micron Gigabit Ethernet length limits were reduced below the 300 meters allowed by the Centralized Cabling TSB-72. By combining all the documents, it became apparent that the “generic cabling system” objective of the 568-A standard was no longer truly generic. Fortunately, similar limitations were not required for 50/125-micron multimode fiber. The inherently larger bandwidth of this fiber type supports Gigabit Ethernet lengths in excess of 500 meters––easily supporting the 300 meters of centralized cabling––at both wavelengths (850 nm and 1300 nm). So, for new installations, standard 50/125-micron fiber with better performance for laser and LED systems can be installed without the need for more expensive fiber, connectors, or electronics. Similarly, the TIA/EIA 568-A standard recommended only one optical fiber connector type––the SC-duplex––and allowed only one other––the ST-style. While these connectors have proven themselves in millions of installations worldwide, their large size and higher cost has limited the acceptance of fiber networks. Over three years ago, several new optical fiber designs were developed in order to reduce connectivity component and installation costs while providing a smaller size. These important characteristics were highly desired in the marketplace, but were not allowed by the governing standard. In order to support the need for smaller and lower-cost connectors while still protecting the end users from poor products, the standards now specify connector performance––regardless of type. Now, as long as manufacturers can demonstrate their product performs to the standard, their connector designs can be used throughout the network. Here again, for new installations, it is possible to provide an optical fiber network at a cost approximately that of a Cat 5e copper network thanks to the reduced connectivity costs. The third principle is centralized cabling. Centralized cabling allows the designer to take full advantage of optical fiber’s benefits by removing the 100-meter restriction of generic copper systems and allowing lengths up to 300 meters––more than enough distance to satisfy the majority of local area network requirements. Because of fiber’s low loss, minimal signal degradation and immunity to RFI and EMI, the flexibility of the optical fiber network is unmatched. Combining these elements––small form factor connectors, 50/125 cabling, and a centralized cabling infrastructure––will result in a very cost-effective, high-performance, flexible, and upgradeable network that is standards-compliant.

Stay Informed Join our Newsletter

Having trouble finding time to sit down with the latest issue of
ELECTRICAL CONTRACTOR? Don't worry, we'll come to you.