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CABLING INFRASTRUCTURE From the July 2006 issue of Communications News |
Plan for adequate LAN bandwidth by Beni Blell and Carol Everett Oliver With the continued rapid expansion of Internet, satellite, wireless and community antenna television services, enterprises are becoming accustomed to two-way, real-time telecommunications. Organizations are now experiencing a convergence of applications, resulting in a truly interactive world. These changes have created the need for would-be content providers to install high-bandwidth enterprise or “first mile” network infrastructures. These networks will likely include fiber-rich campus backbones, data centers and storage area networks (SAN), and enable such new services as distance learning, E-commerce and telemedicine. The infrastructure enhancements within the first mile accurately reflect the fast-evolving dynamics within the access networks, referred to as “the last mile.” Enterprise networks (e.g., universities and hospitals) that are providing new applications, such as remote patient monitoring and real-time, two-way video classes via IPTV, need to build bandwidth capabilities to store, share, retrieve and transmit information to the end-user, through the service provider. Service providers are already offering the “pipes” to deliver high-speed services, including fiber-optic cabling directly to businesses in preparation for multigigabit applications on the horizon.
With all these bandwidth drivers in plain sight, a bottleneck is fast building at the front end (the first mile) of the local area networks within enterprises, many of which do not have the appropriate bandwidth capacity. This could be detrimental to the entire channel. Since no “one-size-fits-all” architecture exists, each enterprise should base its LAN decision on its service goals. The common thread will be a transparent optical network from the first to the last mile. As such, IT infrastructure specifiers, designers and builders should understand that unless the network bandwidth capacity is matched perfectly to that of the arriving infrastructure, eventually it will not be capable to fully exploit future applications. Applications that require a minimum of 10-Gbps transmission capability in the enterprise network include video/telephony/teleconferencing, and search, retrieval and exchange of archived text, audio and video material. Take for example a 30-GB file, which is the size of a standard MRI scan. With a 10-Gbps system, this file can be transmitted in 24 seconds. With a 1-Gbps system, this takes four minutes. Service levels and response times for these types of applications should be maintained at a high level in order to be appealing and usable to the final customer. Fiber is a long-term solution for today’s long- and short-reach applications for the LAN and WAN physical layer–from the first mile out to the end-user. Fiber offers large information-carrying capacity, full symmetric services, long distances, small diameter and lightweight cables, security, and immunity to electromagnetic interference (EMI). What is the correct fiber solution to prepare for future growth? The relevant considerations for selection include: distances, applications and network protocols. Singlemode fiber’s high bandwidth is an advantage when considering its use and distances. With its long reach of 60+ kilometers, singlemode fiber is recommended for WAN, MAN, access and campus backbones,. Singlemode is also incorporated into the network backbone, either within a hybrid cable or using separate cables where compatibility with video applications is a priority. The associated electronics utilizing 1,310-nm and 1,550-nm lasers as the transmitter, however, can cost up to five times more than multimode systems, which employ light-emitting diodes (LEDs) or vertical cavity surface-emitting lasers (VCSELs). For inter- and intra-building backbones, as well as SANs, employing short-wave optics over multimode fiber is the preferred system, mainly due to its lower system cost. Today’s 50/125µm multimode fiber-optic cables are capable of attaining distances of up to 600 meters utilizing 850-nm VCSELs, which are approximately half the cost of comparable 1,310-nm lasers. Although 62.5/125µm multimode fiber-optic cable is still being used for moves, adds and changes, as well as support of legacy networks, its capabilities are short of what today’s 50/125µm laser-optimized multimode fiber can offer. Mixing 50/125µm and 62.5/125µm multimode fiber within the same system is not recommended, however, due to the different core sizes, which increase the insertion loss. When necessary, these two fiber types can be mixed, if there is an active device in between, such as a switch. Some products on the market have standardized on enhanced-performance 50/125µm multimode fiber, which is capable of 750 meters for 1 Gbps and 150 meters for 10 Gbps. Other products offer 600 meters for 1 Gbps. The higher-grade 50/125µm will best assure seamless migration to 10 Gbps for short backbones and even prepare future horizontal systems that will climb to the same speeds. To prepare for the new services and applications that will be possible because of the fiber deployment currently under way, enterprise network designers should focus on the importance of implementing an efficient, scalable cabling infrastructure within the LAN and data center/SAN environments. Whether the network is being built for 1 Gbps or 10 Gbps, the new generation laser-optimized 50/125µm multimode fibers available today can offer better performance over legacy 62.5/125µm fiber options. The choice between singlemode and multimode optical fiber depends on the network services provided and the maximum distance covered. With the inherent high bandwidth and expanding information-carrying capacity, however, laser-optimized 50-micron multimode fiber is the most cost-effective solution within the LAN, data center and SAN for all distances less than 600 meters. Beni Blell is the fiber-optic product business manager for Berk-Tek, a
Nexans company, and Carol Everett Oliver is a Berk-Tek marketing analyst. |