UTP, Optical Fiber, and Future-Proofing

The common networking technologies today (Ethernet, Token Ring, FDDI, and ATM) can all use either UTP or optical fiber cabling, and IT professionals are faced with the choice. MIS managers and network administrators hear much about "future-proofing" their cabling infrastructures. The claim is that installing particular grades of cable and components will guarantee that you won't have to ever update your cabling system again. However, you should keep in mind that in the early 1990s network managers thought they were future-proofing their cabling system when they installed Category 4 rather than Category 3 cabling.

Today, decision makers who must choose between Category 6 and 6A cabling components are thinking about future-proofing. Each category is an improvement in potential data throughput and therefore a measure of future-proofing. Deciding whether to use optical fiber adds to the decision. Here are some of the advantages of using optical fiber:

• It has much higher potential bandwidth, which means that the data throughput is much greater than with copper cable. Optical fiber cable has the potential for higher bandwidth, because it requires a transceiver to deliver the bandwidth. If the highest bandwidth optical transceiver currently available is 10GB, then its actual bandwidth is no better 10GBase-T, notwithstanding the distance capability.
• It's not susceptible to electromagnetic interference.
• It can transmit over longer distances, which is useful for centralized cabling topologies and backbone cabling, although distance is set at 100 meters for the run of cable from the TR to equipment outlets regardless of media, according to ANSI/TIA-568-C.
• Optical fiber also allows the use of telecommunications enclosures, since it can support longer backbone distances than UTP. This essentially places the switches closer to the equipment outlets and can provide savings of approximately 25 percent over the use of switches in TRs. (For more information, see the TIA Fiber Optics LAN Section at www.fols.org)
• Improved termination techniques and equipment make it easier to install and test.
• Cable, connectors, and patch panels are now cheaper than before.
• It's valuable in situations where EMI is especially high.
• It offers better security (because the cable cannot be easily tapped or monitored).

UTP cabling is still popular in a traditional hierarchical topology where an intermediate switch is used in a TR, and you may want to consider remaining with UTP cabling for the following reasons:

• The TIA estimates that the combined installation and hardware costs result in a finished centralized cabling fiber optic network that is 30 percent more expensive than a Category 5e or 6 copper cable network using a traditional hierarchical star topology. However, these cost differences are expected to decrease with time.
• If higher bandwidth (more than a gigabit per second) requirements are not an issue for you, you may not need optical fiber.
• Fiber optics is the medium of choice for security only if security concerns are unusually critical.
• EMI interference is only an issue if it is extreme.

Fiber-optic cabling and transmission media are likely to outpace copper for 100 meter links as speeds increase; however, when considering optical fiber cable, remember that you are trying to guarantee that the cabling system will not have to be replaced for a very long time, regardless of future networking technologies. Some questions you should ask yourself when deciding if fiber optic is right for you include the following:

• Do you rent or own your current location?
• If you rent, how long is your lease, and will you be renewing your lease when it is up?
• Are there major renovations planned that would cause walls to be torn out and rebuilt?

As network applications are evolving, better UTP and optical fiber cabling media are required to keep up with bandwidth demand. As you will see from standards, the end user has many options in a media category. There are many types of UTP and optical fiber cabling. Standards will continue to evolve, but it's always a good idea to install the best grade of cabling since the cost of the structured cabling systems (excluding installation cost) is usually only 5–10 percent of the total project cost. Therefore, making the right decisions today can greatly future-proof the network.

Unshielded Twisted-Pair (UTP)

Though it has been used for many years for telephone systems, unshielded twisted-pair (UTP) for LANs first became common in the late 1980s with the advent of Ethernet over twisted-pair wiring and the 10Base-T standard. UTP is cost effective and simple to install, and its bandwidth capabilities are continually being improved.

Note

An interesting historical note: Alexander Graham Bell invented and patented twisted-pair cabling and an optical telephone in the 1880s. During that time, Bell offered to sell his company to Western Union for $100,000, but it refused to buy.

UTP cabling typically has only an outer covering (jacket) consisting of some type of nonconducting material. This jacket covers one or more pairs of wire that are twisted together. In this chapter, as well as throughout much of the rest of the book, you should assume unless specified otherwise that UTP cable is a four-pair cable. Four-pair cable is the most commonly used horizontal cable in network installations today. The characteristic impedance of UTP cable is 100 \ohms plus or minus 15 percent, though 120-ohm UTP cable is sometimes used in Europe and is allowed by the ISO/IEC 11801 Ed. 2 cabling standard.

A typical UTP cable is shown in Figure 1. This simple cable consists of a jacket that surrounds four twisted pairs. Each wire is covered by an insulation material with good dielectric properties. For data cables, this means that in addition to being electrically nonconductive, it must also have certain properties that allow good signal propagation.

Figure 1: UTP cable

UTP cabling seems to generate the lowest expectations of twisted-pair cable. Its great popularity is mostly due to the low cost and ease of installation. With every new generation of UTP cable, network engineers think they have reached the limits of the UTP cable's bandwidth and capabilities. However, cable manufacturers continue to extend its capabilities. During the development of 10Base-T and a number of pre–10Base-T proprietary UTP Ethernet systems, critics said that UTP would never support data speeds of 10Mbps. Later, the skeptics said that UTP would never support data rates at 100Mbps. After that, the IEEE approved the 1000Base-T (1 Gb/s) standard in July 1999, which allows Gigabit Ethernet to run over Category 5 cable. Just when we thought this was the end of copper UTP-based applications, in 2006 the IEEE approved the 10GBase-T standard, which allows 10 Gigabit Ethernet over unshielded Category 6 and 6A cable!