with white, and brown with white. www.TechnicalPDF.com www.TechnicalPDF.com Figure 1-4 Unshielded twisted-pair cabling used within enterprise buildings. (Photo by Annabel Z. Dodd) UTP copper and fiber-optic cables are the most common media used in enterprise LANs. Because of improvements in the speeds, capacity, and distances wireless signals can be transmitted, wireless media is replacing copper cabling in some office buildings. Wireless services based on the 802.11 (Wi-Fi) protocols are discussed in Chapter 7, "Mobile and Wi-Fi Networks." Characteristics of media have a direct bearing on the distance, speed, and accuracy at which traffic can be carried. For example, thin copper wire carries data shorter distances at lower speeds than thicker, higher- quality copper. In corporate networks, UTP is the most prevalent medium used to link computers, printers, and servers to wiring closets on the same floor. This is referred to as the horizontal plant. Fiber is capable of carrying vastly more traffic than copper. However, it is more expensive to install and connect to devices in LANs than UTP, and thus it is generally used in high-traffic connections between the following: Wiring closets Floors (the risers) Buildings on campuses The key characteristic that makes fiber suitable for these high-traffic areas is that it's a non-electric medium. Fiber exhibits superior performance because, unlike copper, it does not transmit electric signals that act like www.TechnicalPDF.com an antenna and pick up noise and interference from nearby electrical devices. Connecting Fiber to Copper In enterprise networks, when fiber is connected to copper cabling at locations such as entrances to buildings, at wiring closets, or in data centers, equipment converts light pulses to electrical signals, and vice versa. This requires converters called transmitters and receivers. Transmitters also are called light-source transducers. If multiplexing equipment is used on the fiber, each channel of light requires its own receiver and transmitter. Tr