Picking the Right Cable for the Job

Professional cable installers and cable-plant designers are called upon to interpret and/or draft cable specifications to fulfill businesses' structured-cabling requirements. Anyone purchasing cable for business or home use may also have to make a decision regarding what type of cable to use. Installing inappropriate cable could be unfortunate in the event of a disaster such as a fire.

What do we mean by unfortunate? It is conceivable that the cable-plant designer or installer could be held accountable in court and held responsible for damages incurred as a result of substandard cable installation. Cables come in a variety of ratings, and many of these ratings have to do with how well the cable will fare in a fire.

First, you must know the installation environment and what the applicable NEC and local fire-code requirements will allow regarding the cables' flame ratings. In a commercial building, this usually comes down to where plenum-rated cables must be installed and where a lower rating (usually CMR) is acceptable.

Your second decision on cabling must be on media type. The large majority of new installations use fiber-optic cable in the backbone and UTP cable for the horizontal.

For fiber cable, you will need to specify single-mode or multimode, and if it is multimode, you will need to specify core diameter—that is, 62.5/125 or 50/125. The large majority of new installations utilize an 850nm, laser-optimized 50/125 multimode fiber (TIA-492AAAC-A); better known to the industry as OM3 fiber (per ISO/IEC 11801 Ed. 2). For UTP cables, you need to specify the appropriate transmission-performance category. Most new installations today use Category 6, and there is a growing migration to Category 6A. Make sure that you specify that patch cords be rated in the same category as, or higher than, the horizontal cable.