Consulting-Specifying Engineer - August 2008 - (Page 62) Equipment Lifecycles Unlike a commercial environment, industrial environments vary depending on the industry; each environment represents specific conditions that the engineer must consider. The considerations for a power generation plant are different than those for a micro-electronics manufacturing facility. In a power generation facility, the designer needs to consider the impacts of temperature variations, large magnetic fields, and areas of very high voltages. In a micro-electronics manufacturing facility, the designer may need to consider exposure to chemicals, high radio frequency exposure, and the impact of the cable itself to a clean room environment. The commercial environment In a typical office building or similar space, 100BaseT and 1GBaseT Ethernet are still the most popular protocols used on the network. These protocols support the bandwidth for most office-type applications because 1GBaseT is able to support network bandwidths to the desktop for the next 5 to 10 years. Cat 5e and Cat 6 will support these protocols; Cat 5e cable is the less expensive of the two. Although both of these cable types will support the same types of Ethernet, the Cat 6 cable is rated to a higher frequency with higher performance characteristics. When the networked starts to get stressed due to high-bandwidth applications, the Cat 6 cable may have more tolerance for the installation and component abnormalities that tend to affect performance. If you think you have issues with the quality of the installation or the electromagnetic interference (EMI) noise in the environment, a Cat 6 cable with its additional headroom in performance might be worth the added cost. When specifying a Cat 5e cable that you plan to work at 1GBaseT and last for the next 8 years, consider the purchase of top-tier components. Some cable manufacturers don’t make their own termination components, but these companies usually have warranty agreements with companies that do manufacturer the jacks and patch panels. With any of the cable types noted here, abide by manufacturers’ warranties and use certified installers. Table 1 Cable type Cat 5e Cat 6 Cat 6 Cat 6 shielded Cat 6a 62.5/125 micrometer multimode fiber optic cable, standard grade 50/125 micrometer multimode fiber optic cable, Laser Optimized** 150 Cable channel distance 100 meters 100 meters 55 meters 100 meters 100 meters 300 meters* 550 meters* 750 meters* 600 meters* 150 meters* Ethernet protocols 10BaseT, 100BaseT, 1GBaseT 10BaseT, 100BaseT, 1GBaseT 10GBaseT 10BaseT, 100BaseT, 1GBaseT, 10GBaseT 10BaseT, 100BaseT, 1GBaseT, 10GBaseT 1G Ethernet (850nm) 1G Ethernet (1,300nm) 1G Ethernet (850nm) 1G Ethernet (1,300nm) 10G Ethernet (850nm) * TIA/EIA 568.B does not allow a horizontal pathway to exceed 100 meters, although the Ethernet protocol for fiber optic cable allows for cable channels beyond 100 meters. ** Laser Optimized is a trademark of Corning Cabling Systems. What about Cat 6A, Cat 6 shielded, or fiber optic cable to the desktop? There are some desktops that could use 10GBaseT to the workstation, but these are rare circumstances. If you are planning for an installation to last 10 to 15 years, then one of the above choices may make sense in allowing a migration to 10GBaseT. With these types of cables, there is more to consider than just cable and termination cost. For Cat 5e and 6 cable, the Cat 6 cable material will cost more, but the cost of labor and the impacts to cable tray and conduit fill are about the same. When considering the Cat 6 shielded and Cat 6a cables, it also is important to note that the cable diameters are larger. The nominal diameter of Cat 6 cable is 0.2 in.; the diameter of a Cat 6a cable can be 0.31 in. (Some cables are larger or smaller, depending on the manufacturer.) This increased size of the Cat 6a cable will affect the sizing of cable trays and pathways in order to support the larger cable. For example, a 6x12 in. tray filled to 50% with Cat 6 cable of a nominal cable diameter of 0.2 in. would hold about 1,200 cables. The same number of cables for a Cat 6a cable with a nominal diameter of 0.31 in. would require a cable tray size of 6x30 in. That is a significant increase in cable tray size and cost. Fiber optic cable has its own pros and cons. A four-strand fiber optic cable is no larger then a Cat 5e cable at 0.19 in. diameter. The cable itself is really no more delicate than the twisted-pair cables, although kinking a fiber optic cable may cause it to break, while kinking the twisted-pair cable may cause only poor performance. The fiber optic industry has come a long way in developing easy and quick fiber terminations that can be made in the field. The cons for fiber is the cost of the electronics to convert the optical signal back into an electrical signal. Another consideration is that the optical 62 Consulting-Specifying Engineer • AUGUST 2008
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.