Q: I have been working in the design and installation of structured cabling for many years and have experience with unshielded and shielded twisted-pair cable and fiber-optic cable. To date, I have installed fiber only as a backbone. Now I am involved with a fiber-to-the-desk project with about 200 workstations. What are the advantages and disadvantages of this type of application?
Mario Dual Cotera
Enlace de Datos SA de CV
Mexico, DF
A: Twenty-five years ago, Moore`s Law stated that the number of transistors on a microprocessor would double every 18 months, and with it, the speed at which data is transmitted. Moore was correct.
I believe that fiber is the only long-term choice of cabling medium. I have been recommending fiber-to-the-desk at the University of Texas at Austin for some time, but the university`s funding model has not supported the additional cost of the fiber medium and the associated network hardware. So, for the last six years, I have been specifying cabling infrastructure pathways that will support both the copper cabling of the present and the fiber-to-the-desk of the future into our new capital projects, while installing the highest category of cable that I could convince my management to fund.
Many colleges and academic departments whose buildings were cabled with Category 3 cable in the late 1980s and early 1990s are already requesting estimates to recable their buildings with Category 5 cable. At that point, I dust off my "fiber-to-the-desk" speech and attempt to convince the decision-makers to wait until fiber hardware costs come down. (The cost of optical fiber is much easier to cost-justify today than it was just a few years ago.)
Because most campus networks are just upgrading from LocalTalk to 10Base-T, with a few 100Base-T ports for the servers, we recable to the servers with Category 5 cable--and we wait.
Fiber has the largest bandwidth of any medium available, can transmit signals over the longest distance, is immune to electromagnetic and radio-frequency interference, and is not easily tapped. Given these advantages, the designer can choose to collapse the network into one closet and install fiber cables from this closet to each work area in the building. This eliminates the need for multiple telecommunications closets on each floor. Reducing the number of closets in a building saves money and space by reducing the number of locations that must be outfitted with additional power, heating, ventilating, and air-conditioning facilities. Network management is centralized, reducing the number of maintenance or troubleshooting locations and allowing for more efficient use of hub equipment. Testing and documentation also become less cumbersome.
The disadvantage of fiber is the increased cost of the medium and associated hardware over copper-based solutions.
Donna Ballast is a communications analyst at the University of Texas
at Austin and a bicsi registered communications distribution designer (rcdd). Questions can be sent to her at Cabling Installation & Maintenance or at PO Drawer 7580, University of Texas, Austin, TX 78713; tel: (512) 471-0112, fax: (512) 471-8883, e-mail: ballast@utexas.edu.
