If 10-Gigabit is in Your Future, Plan for Cable Pathways

Installing a 10-gigabit (10G/s) system requires that careful attention be paid to cabling pathways. It is more critical than ever that every aspect of the structured cabling system, including pathways, be designed to ensure the highest channel performance. All pathways must accommodate new cable designs, specifically the cable diameter, the weight of the cable, and its minimum bend radius.

Building system designers employ a variety of wire and cable management pathways to provide optimal cabling flexibility (see sidebar). However, today's familiar pathways may not be adequate for such new technologies as "augmented" Category 6 (Category 6a) cable.

Next Generation Cable

Standard Category 6 cable does not allow 10G/s transmission beyond a distance of about 55 meters. Category 6a cable is designed to support 10G/s at 90 meters. To provide this higher performance over longer distances – without adding shielding – the cable was redesigned to reduce the effects of alien crosstalk (electrical noise from outside a cable). Category 6a UTP (unshielded twisted pair) cables have larger overall jackets that isolate twisted pairs from adjacent cables and reduce alien crosstalk.

Other 10G/s cable options include the use of a layer of foil within the cable (e.g. Category6 FTP) or integral shielding or screening (e.g. Category 7 STP, Category 7 ScTP). The diameter and bend radius of these cabling options have an impact on the design of the cabling pathway.

Cable Diameter Bend Radius
Category 6 0.225" (5.72 mm) 1.25"
Category 6a 0.354" (9 mm) 1.5"
Category 6 FTP 0.285" (7.24 mm) 2.28"
Category 7 STP 0.330" (8.38 mm) 2.64"

The difference in diameter between Category 6 cable and Category 6a cable may seem trifling, but it has a significant impact on the number of cables that can be accommodated in a particular pathway. For example, a 0.75” (21 mm) conduit will hold four Category 6 cables, but only one Category 6a cable at 40 percent fill. Similar capacity reductions are noted for other cabling pathways. System designers should be aware that changes to the TIA-569-B pathways and spaces will no doubt include new fill capacities for perimeter raceway systems, cable trays, furniture systems, and other pathways.

The larger bend radius of 10G/s cables also requires more space – in telecommunications rooms, horizontal pathways, and at the workstation – to avoid creating tight bends that degrade performance. Pathway size is an important consideration when planning a 10G/s network.
In addition, next generation cable is heavier than the cable that is currently in use. And, since its greater weight makes Category 6a cable more difficult to pull, pathways that offer lay-in installation may be preferable both for initial installation and to accommodate moves, adds, and changes.

The cabling pathway extends from the main equipment room, to the risers, to telecommunications rooms, to horizontal cable management, to the workstations. The impact of larger, heavier, and more bend-sensitive cables must be considered at every point along the pathway. Even if you are not installing a 10G/s cabling system today you must think of the future. Pathways and spaces are static components that have a life expectancy far great than that of the cabling system. So long-term planning is always a wise choice.