Published In October 2001
There are many options when choosing the correct cabling media for your network installation. Category 5e, Enhanced 5e, Category 6, single-mode, and multimode fiber are among the selections you have. You will make the best decision by understanding the strengths and weaknesses of each of the different types of cables. In the world of premises infrastructure, copper is dominant in the horizontal pathways of buildings. It is said that 80 percent of the world’s buildings are cabled with unshielded twisted pair (UTP) cabling. UTP installation is understandable and simple, the cables are small and easy to pull, and the connectors can be quickly terminated. Scores of manufacturers build products that depend on UTP to transmit their signals. Data speeds have increased from 10 Mbps to 100 Mbps and most recently to 1,000 Mbps. UTP cables such as Category 5e and now Category 6, with its greater bandwidth, have the capability to support these speeds and go even faster when the time comes. What about fiber in horizontal building applications? When the TIA-568 documents were being developed, fiber was originally excluded from the list of recommended horizontal media until forward-thinking individuals fought to add it. It is now 11 years later, and although fiber features greater data-carrying capacity than copper, fiber has not infiltrated the horizontal cabling market as anticipated. Although the resistance to fiber is weakening, there are still significant obstacles to overcome. Advancements in connector design have simplified fiber cable termination, but even with improvements in craft, the total installation cost is higher than it is for the typical copper installation due to the cost of the active equipment. To reduce the amount of electronics required in a system, TIA introduced the concept of centralized optical fiber cabling. This eliminates the need for active equipment on each floor in a building and helps to reduce installation cost. Even with TIA’s effort, the acceptance of fiber in the horizontal is still a small percentage of the overall picture. Fiber is king for long-distance backbone cabling. Backbone distances can vary from just a few feet to hundreds or even thousands, depending on the installation. When the distances are longer than 295 feet, fiber is an absolute requirement. And if you’ve decided to use fiber in your network, then do you use single-mode or multimode fiber? Choosing the right fiber requires knowledge of the installation, the distance of each fiber optic link, and the applications that the customer is planning to run over the life of the building. In the simplest terms, if the distances are relatively short (less than 900 feet) and the customer does not anticipate moving to very high-speed applications like 10 Gigabit Ethernet, then conventional 62.5 micron fiber is perfect. If the customer is more sophisticated, has longer distances, and sees the need to run the backbone as fast as possible, then an enhanced multimode or even single-mode should be considered. Conventional Category 5e or Category 6 cables can be used for distances shorter than 295 feet. Again, the short- and long-term needs of the customer must be weighed if UTP is chosen as the media to transmit data. Although UTP cables are an economical choice and can handle data transmission up to 1 Gigabit per second, this type of cable is limited to applications inside single buildings due to the distance limitation. TIA 568-B states that the cabling infrastructure is expected to have a useful life in excess of 10 years. When choosing between copper and fiber media for the installation and application, the requirements of the customer must be considered to make the correct decision. Copper is predominant in horizontal installations and will continue to be so for the foreseeable future. Very high-end customers with lots of future bandwidth needs who are trying to stretch the life of their system well beyond 10 years are considering fiber. In the backbone, except in the simplest and smallest installation, fiber is used. The choice of what fiber to use is based on knowledge of the installation and future needs of the end user. DEBIEC is technical training manager at Berk-Tek. He can be reached by e-mail at firstname.lastname@example.org.