Optical fiber has become the preferred media for transmitting voice, data, and video over Local Area Networks (LANs). However, traditional fiber-optic cable installations pose multiple challenges for LAN administrators. First is the difficulty of forecasting future requirements for routing, capacity, and fiber types. Then, of course, comes the challenge of actually installing the LAN. Once the network is installed, MIS managers face the labor, expense and network disruptions that occur when the inevitable moves, additions and changes (MACs) have to be made.

As MIS managers in many corporate offices, universities, hospitals, and other facilities will attest, MACs are a way of life, necessitated by expansion, changes in space allocation, and changing network needs. But with every change or reconfig-uration of a traditional fiber installation, they run the risk of compromising signal integrity and network performance because of too many splices and connections.

System designers and electrical contractors should know about an alternative solution called air-blown fiber (ABF). An innovative fiber-optic network cabling technology, ABF allows all the benefits of fiber-optic transmission to be achieved without the maintenance costs and transmission quality risks. Because of its reliability, ABF is also being deployed for HVAC, security, and life and safety systems. Current users include the Pentagon, U.S. military bases, the Getty Center in Los Angeles, Las Vegas hotels and casinos, Kaiser Permanente, and other health care facilities, corporate campuses, manufacturing and processing plants-and schools and universities.

How ABF technology works

An ABF cabling system is composed of an infrastructure of rugged, flexible tube cables used in place of traditional innerduct. Each tube cable contains up to 19 coded tube cells. The cells are joined in tube distribution units (TDUs) or junction boxes by using push-fit connectors to provide a direct route between the network hub and the application. The TDUs replace conventional fiber splice hardware at tube cable transitions and branching locations.

Once the infrastructure is in place, lightweight bundles of single or multimode fiber are blown through a predefined route on a stream of compressed air or nitrogen, using a special blowing head device. Installation is fast and simple. The fiber is blown at speeds up to 150 ft per minute and can easily be accomplished by twotrained technicians. Cable runs may exceed 6000 ft, and the fiber path may traverse outdoor, riser and plenum tubes in a single run.

Because the fibers are never pulled, no strain is exerted to cause immediate or future degradation. And, with point-to-point connectivity directly from the computer room or network hub to the application, ABF technology improves overall system reliability and provides optimum fiber performance.

In almost all ABF installations, tube cable is installed with more cells than are currently required to ensure room for expansion. Unused cells are simply capped off within the TDUs. Network expansion or reconfiguration is accomplished simply by extending tube cables from the nearest TDU. Fiber changes are done by blowing cable through unused cells, or by blowing out old fiber (which can be reused) and blowing in new-all without disruption to the existing network. ABF fiber bundles are significantly smaller and take up far less space than conventional cables, an added benefit where tray or conduit space is a factor.

ABF cabling systems are ideally suited to large or highly complex network configurations, as well as to dynamic LANs requiring frequent changes. In addition, ABF technology protects the technology investment by providing an extremely cost-effective approach, coupled with optimum performance and flexibility.

Bandwidth skyrockets at a California university

From an investment point of view, the University of California, Riverside (UCR), is a prime example of the cost-saving advantages of ABF. UCR saved $2.5 million over four years by switching from a conventional fiber optic communications system to Sumitomo Electric Lightwave's FutureFLEX air-blown fiber optic cabling system. An additional cost savings of $500,000 is anticipated over the next five-year period through reduced MAC expenses.

As in many large university campuses, the demand for bandwidth on fiber cable at UCR has skyrocketed in recent years. In addition to an increased number of telephones and modems, university departments and offices are interconnected via LANs, and the Internet has become an increasingly useful academic tool for faculty and students alike. Anticipating growth of enrollment from less than 10,000 students in 1996 to 15,000 in 2005 and nearly 30,000 by the mid-2000s, UCR wanted to be ready to support this expansion with a future-proofed communications system.

In its first large-scale use of ABF technology in the mid-1990s, UCR found the cabling could be installed in about one- third of the time and with less labor than required for conventional fiber cabling. ABF also provided the university with a multiple routing scheme and enormous surplus capacity. Initially, the campus was using only 10% of the network's capacity. Yet UCR spent only $692,000 and four months installing the ABF system compared to an estimated cost of $3.2 million and 12-month installation for a conventional fiber system.