Blown Fiber Changes Installation Rules For Two Schools
Flexible cable-installation process allows frequent changes for classroom computer upgrades
by C.S. Pegge

Blown fiber is breaking rules and records for classroom computer network cabling. More flexible than conventional fiber-optic cable, blown fiber speeds installation and allows for frequent MACs (moves, adds and changes) without recabling. Basically, the blown-fiber process is as simple as it sounds--just blow out the old fiber and then blow in the new. It's all done through empty, flexible plastic tubes.

School districts and colleges are ahead of the learning curve in adopting blown fiber. Two recent extensive installations of blown fiber happened at a large middle school in Wellesley, Mass. and at public schools in Wake County, N.C.

"Education is a top priority to the parents and people of Wellesley," said Tom Plati, director of libraries and educational technologies for Wellesley Public Schools. "Their support enables us to provide technology infrastructure, resources and capabilities to all of our students."

LCN Inc., a local computer network designer and installer, won the Wellesley public school bid of nearby Weymouth, just south of Boston. LCN proposed using blown fiber technology to install the network backbone at Wellesley Middle School.

"Right away I thought that blown fiber would be the perfect way to build future capacity for this installation," said Tyrone Sandefur, project manager for LCN on this job. "Many schools, especially older buildings, are built like fortresses. Blown fiber is simply a much easier way to handle installations in that sort of situation."

Bill Alessi, LCN foreman, said that the network backbone included eight singlemode and eight multimode optical fibers. "We blew in fibers from the MDF (main distribution frame) to four IDFs (intermediate distribution frames) in a matter of minutes."The length of the run was 610 meters. "Instead of having to pull cable through conduit, the fibers just flew through the tubes effortlessly, certainly with a lot less complicated effort on our part," Sandefur said.

LCN President Mike Lieb envisions blown fiber as an increasingly popular option for network cabling installations. "As clever as blown fiber technology may be, this isn't a gadget or a fluke," Lieb said. "For many real world applications, blown fiber will be the best solution."

In one of the largest public school divisions in North Carolina, Wake County public schools serve the cities of Raleigh and Cary and surrounding communities. Like Wellesley and the Boston area, the region is likewise a locus of higher education--home to North Carolina State University and neighbors of Duke University in Durham and the University of North Carolina in Chapel Hill.

Wake County public schools' commitment to the Internet and computer technologies would entail installing network infrastructure that would require wiring more than 100 school buildings, including some campuses with multiple sites. Typically these school facilities occupy from 75,000 to 80,000 sq ft, each a local area network or branch in itself.

Highly regarded engineering and design firm Dewberry & Davis won contracts to perform campus-wide wiring upgrades at more than 100 schools in Wake county. Dewberry & Davis is headquartered in Fairfax, Va, and maintains offices in Raleigh and 27 other cities throughout the region.

"Including retrofit and new construction for many sites and buildings, this is a big job and a top priority for a public school system," said Glen E. Ellmers, P.E., senior associate and branch manager of the Raleigh office of Dewberry & Davis. "There is much work to be done in a short time, and this is happening in school districts all across the country."

"Given the time factor, this is a perfect example where quicker and easier blown fiber installation for the network backbones makes practical sense," said Cash E. Davidson, P.E., senior electrical engineer at Dewberry & Davis.

The installer on the job is Ambassador Enterprises, Inc. based in Portsmouth, Va., also with satellite offices in Raleigh, Charlotte and Roanoke.

"Generally we're now tackling these wiring installations in group of four to six schools, or maybe 10 buildings at a time," said AE President Randy Vaughan. "Once you know what you're doing, blown fiber installation can be a much simpler way to get the job done, particularly in older buildings."

"Blown fiber will continue to provide a real advantage to our client," Davidson said. "And that's what it's all about--bringing better ideas and solutions to clients is why we're here."

Unlike other optical-fiber technologies blown fiber will not be outmoded by new developments and innovations. On the contrary, with blown-fiber infrastructure, the ability to accommodate change is built into the basic design. Change is part of the plan.

The benefits of blown fiber Blown fiber technology was originally developed by British Telecom and quickly became popular in the U.K., Western Europe and Asia. Unlike conventional optical fiber, blown-fiber systems begin with the installation of empty, flexible plastic tubes. The small tubes, known as microduct, come in 5 mm and 8 mm diameters and are approved for riser, plenum or outside-plant applications. Microduct installs easily, especially in spacious older facilities. Coated "blowable" optical fibers are then blown in through the microduct using compressed air. Carried by viscous drag, the fibers are lifted into the airstream and away from the wall of the microduct, thereby eliminating friction even around tight bends. In a relatively short period, coated fibers can be blown for distances up to one kilometer (3281 ft) in a single run--or around 300 small-radius right-angle bends. Blown fiber systems, such as General Cable's own Blolite, reduce both the initial investment and the costs over time. For example, blown fiber customers can first install fiber-optic network backbones with high performance copper wiring to the desktop, then "fly" fiber to the desktop with blown fiber when that option becomes more practical and affordable. That means network designers don't have to future-proof every possible network branch and contingency. In addition, MACs no longer require recabling or all new cable installation. Instead, just blow out the old fiber and blow in the new fiber. Since being developed by Corning, most fiber-optic cable design has centered around protecting optical fiber from elements and, more importantly, from damage during installation. Fiber can be stretched out of shape while being pulled through conduit. In addition, fiber-optic cables that form many network backbones often contain unused optical fibers to meet any possible future technology requirements, a strategy commonly known as "future-proofing." The cost, however, includes adding that extra fiber capacity at the beginning to provide extra bandwidth for future computer upgrades.

 

Reprinted with permission from the August 1999 issue of CEE News®.

Copyright 1999, Intertec Publishing, A PRIMEDIA Company, Overland Park, KS. All rights reserved.

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