Tài liệu TRANSITION TO THE NEXT GENERATION docx

Cabling Infrastructure TRANSITION TO THE NEXT GENERATION The emergence of 10-Gigabit Ethernet (10- GigE) began with a surge in demand from data centers and information-hungry markets, such as higher education, financial management, healthcare, engineering design, research and development, and government institutions. Today, the acceptance of Gigabit Ethernet mov- ing to the desktop drives the need for 10-GigE in the backbone. While deployment and system upgrades sound simple enough, careful consideration should be given to a number of factors when choosing how and what components should be used to ensure the infrastructure supports the protocol today and in the future. Most campus and building backbones today are hybrids, meaning they contain both multi- mode and single-mode fibers within the same cable sheath. The proportion of multimode to single-mode will vary depending upon the organization’s current and future expectations for distance and bandwidth capacity. Single- mode fiber is only limited in bandwidth by the electronics that it connects. Within the typical LAN, however, most topologies can effectively be deployed over multimode fiber. For 10-GigE, attention should be focused on laser-optimized 50/125, which is ideal for 10GBASE-SR, the most cost-effective derivative of the 10-GigE standard. Coarse wavelength division multiplexing (CWDM) will be used extensively in the future to increase bandwidth. Low water peak single- mode fiber should be used with CWDM net- works, as it produces a flattened attenuation profile and improves transmission. In short, using the proper multimode and single-mode fibers effectively ensures that your network will support the next leap in technology, and pro- tect the longevity of the cable plant. Connectivity is the single most overlooked component of the cabling infrastructure. While the connector type is not the most critical fac- tor, the end face preparation of the connector is crucial for optimizing high-speed systems. A poorly prepared connector can devastate net- work performance, resulting in numerous prob- lems and inadequate data throughput. A poorly polished connector equates to lost data, and is an important consideration when working with multimode assemblies. For this reason, factory-polished connectors make the transition to 10-GigE simpler and more reliable. These preterminated assemblies, or pigtails, are manufactured in an advanced and dedi- cated environment where critical end face ge- ometry measurements can be consistently re- peated and tested. When field terminating fiber connections, connectors should be specified with the tightest tolerances for better fiber placement within the ferrule. This will limit insertion loss and facilitate an easier transition to mul- tiplexing schemes. As small form-factor connectors continue to proliferate, the density of terminations within fiber panels is effectively doubling. This makes the difficult and vital task of properly managing cables and patch cords even more imperative. This article was provided by Kam Patel, the director of support technologies for ADC, Eden Prairie, Minn. He holds a degree in electrical engineering and has more than 13 years of experience in the fiber-optic industry. Regardless of the connector type, the most important selection criteria for optical mount- ing and management hardware should be bend radii and cable slack control for the cables and patch cords. Throughout the entire channel, from port to port, appropriate cable manage- ment should be observed. The most flexible patch panels are those that are modular in design, allowing for different connector types, as well as different fiber types within the same panel. Consider implementing patch panels that are sold preloaded with pig- tails to make the installation faster and more reliable. Make sure that technicians can easily access individual connectors to manage cir- cuits without disrupting adjacent connections. Choose cable tray systems that protect fiber integrity and limit bends. Quality cable trays should be adaptable to custom requirements, with options for varying cable density and cable entry and exit points. In addition, remember such details as compo- nent placement. For example, fiber patch pan- els should be placed at the top of the rack with a minimum of 10 feet of management slack. Finally, keep in mind that copper cables are heavier than their fiber counterparts, so, whenever possible, separating the copper and fiber cabling is recommended. Although fiber cables are robust, they are susceptible to damage if not properly cared for during the installation process. For more information from ADC: www.adc.com Reprinted from Communications News , August 2005 Copyright © 2005 by Nelson Publishing Inc. • www.comnews.comLit.#: 1339339 . and government institutions. Today, the acceptance of Gigabit Ethernet mov- ing to the desktop drives the need for 10-GigE in the backbone. While deployment. given to a number of factors when choosing how and what components should be used to ensure the infrastructure supports the protocol today and in the future. Most