Monday, August 1, 2011

Horizontal and Backbone Cables

The terms horizontal cable and backbone (sometimes called vertical or risercable have nothing to do with the cable's physical orientation toward the horizon. Horizontal cables run between a cross-connect panel in a telecommunications room and a telecommunications outlet located near the work area. Backbone cables run between telecommunications rooms, and enclosures, and the main cross-connect point of a building (usually located in the equipment room). Figure 1 illustrates the typical components found in a structured cabling environment, including the horizontal cable, backbone cable, telecommunication outlets, and patch cords.

Figure 1: Typical components found in a structured cabling system

Horizontal Cables

Horizontal runs are most often implemented with 100 ohm, four-pair, unshielded twisted-pair (UTP), solid-conductor copper cables, as specified in the ANSI/TIA-568-C.2 standard for commercial buildings. The standard also provides for horizontal cabling to be implemented using 62.5/125 micron or 50/125 micron multimode optical fiber. Optical fiber is typically used when electromagnetic interference (EMI) or radio-frequency interference (RFI) is a problem and when security is critical. Coaxial cable is not a recognized horizontal cable type for voice or data installations.

Backbone Cables

Backbone cables can be implemented using 100 ohm UTP, ScTP or STP; 62.5/125 micron or 50/125 micron multimode optical fiber; or 8.3/125 micron single-mode optical cable. Neither 150 ohm STP nor coaxial cable is allowed. Optical fiber is the preferred cabling medium because of distance limitations associated with copper wiring (90 meters is the maximum distance). Optical fiber cable can transmit over distances up to 40,000 meters depending on f


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