The spread of Internet-related technology is creating new challenges for managers

The spread of Internet-related technology throughout facilities is creating installation and maintenance challenges. Maintenance and engineering managers also are encountering added challenges as they are called upon to install, update and maintain increasingly complex cabling and wiring systems. Staying on top of these challenges starts with understanding the basic types of wiring and cabling systems, as well as the relating parameters and standards.

Fiber and copper
Most communication wiring and cabling is either fiber or copper. There are three types of copper cables used in communication applications, namely coaxial cable, shielded twisted pair (STP), and unshielded twisted pair (UTP). Coaxial cable systems, the workhorse of the industry, can accommodate longer distances at higher data rates.

A coaxial system also inherently has a self-shielding capability that reduces its vulnerability to interference. Today, with technology advancements in twisted-pair cable technology, coaxial use is limited to installations that cannot be accommodated by twisted pair wires.

Shielded cable uses either a thin overall outer foil or a heavy braided shield. STP provides better signal protection against interference and supports higher data transmission rates than UTP. But for STP to be effective every component and connector in the system should be fully and seamlessly shielded.

Because of these complications, STP is used only in specialized cases. Today, for most applications, UTP has become the most popular type of copper wiring in the industry. Since UTP does not rely on physical shielding to stop interference, it is a more robust system. UTP is easier to install and inherently has fewer points of failure compared to STP.

The primary median for a communication backbone system is fiber, which can transmit signals over the longest distances at the lowest cost. The size of fiber cable is more than an order of magnitude smaller than copper cable.

The diameter of single-mode fiber is 0.000472 inches, which is about one-tenth the diameter of a human hair. For instance, network segments can be 20 times higher than copper and can support several gigaHertz (GHz) of optical bandwidth. Also, fiber can accommodate the widest bandwidth and is immune to electromechanical interference and radio frequency interference.

Since it is difficult to tap into fiber, it provides a highly secure and reliable system. Finally, fiber is not affected by crosstalk, lightning strikes or ground-loop currents.

Fiber cables are two types, single mode and multimode. Single mode has a small core of about 5- 10 microns, it has a higher capacity, and it is used for longer distances than multimode. Single mode is mainly used by telephone company switch-to-switch connections and cable television, as well as wide area networks.

Multimode is thicker and has a core diameter of 62.5 microns. It is used for local area networks where the distances are less than 1.2 miles.

Network installation
In the past, as an enterprise's network requirements changed, it was not unusual to employ a new communication cabling system. The need for high-speed Internet service provider (ISP) and e-commerce capabilities is becoming standard requirements for an increasingly larger number of enterprises.

Today, with constant upgrades and changes of network requirements, it is impractical and highly uneconomical to replace cabling continuously. In other words, managers should view the communication backbone as a utility that can be easily adapted to new technology upgrades. Managers can meet the need for easier migration to new network requirements using a structured cabling system.

Unlike proprietary data networks, structured cabling can support vendor-independent interconnections for many networks, hubs, routers, bridges and switches. The basic requirements of structured cabling are covered by TIA/ EIA-568-B standards for electrical, optical and mechanical inter operability of various physical layers.

A structured cabling system uses a star topology because of its high functionality. The center of such a cabling system is the main distribution center, which is interconnected using a fiber backbone with a number of intermediate distribution centers (IDC). Similarly, many telecommunication closets are connected to the IDC.

Managers should carefully determine the location of wiring closets to minimize wiring runs. In renovation projects, exiting telephone closets are usually the first candidate for this application. Cable runs commonly are located within the structural floor. In larger buildings, a raceway is used to provide mechanical support and protection for cables.

Also, for renovation projects, when it is not economically or structurally feasible to install a concealed system, managers can consider using surface-mounted systems with baseboard raceways, molding raceways, over-floor ducts, or flatwires. Flatwires typically are installed under carpets.

Finally, it is important to note that most electronics used for communication systems today become obsolete in two to three years. The communication cables especially using structure systems can last for 10 years or more, but conduits and cable trays used will last 20-30 years or longer.

So, it behooves managers to pay close attention to the initial planning and routing of cable trays and conduits in order to be able to utilize the asset fully.

Maintenance and Troubleshooting
Ongoing maintenance of cabling system is important for every facility. Some of the common testing equipment for copper cables are these:

a wire map tester, which can check for open or short circuits as well as reverse pairs, crossed pairs or split pairs.

the above article was written by Mohammad Qayoumi, P.E.who is author of The Metering Guide for Managers, published by The association of Higher Education Facilities Officers (APPA) and appeared previously in the November 2001 issue of Maintenance Solutions.



First published December 2001

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