The Installation of fiber optic cable is a very broad subject, mainly because every project is different. Proper installation requires good judgment, patience and care in handling the cable. Instead of trying to cover all installation types, let’s examine some guidelines that can be applied in most.
Fiber optic cable, hardware and supplies should be scheduled for delivery to the work site as close to the time of use as possible to minimize possible damage from other construction, weather or theft. When received, all fiber optic cable should be carefully inspected for damage and tested for continuity or loss if damage is suspected.
Handle reels of fiber optic cable with care to avoid damage to the cable. Move small, lightweight spools of fiber optic cable by hand. Move larger reels with appropriate lifting equipment or using two or more installers skilled at moving.
All equipment and cabling should be stored in a clean and dry location and protected from harsh environments, such as extremes of cold and heat. Due to the value of the cable and potential for theft, all components should be in secure storage with guards provided when necessary.
Check the cable length to ensure the cable being pulled is long enough for the planned cable run. Try to complete the installation in one pull, if possible. Prior to any installation, assess the route carefully to determine the methods of installation and obstacles likely to be encountered.
Follow the cable manufacturer’s installation recommendations. Fiber optic cable often is custom-designed for the installation, and the manufacturer may have specific instructions on its installation.
Cable manufacturers install special strength members, usually aramid yarn (Dupont Kevlar), to absorb the stress of pulling the cable. The cable should only be pulled by these strength members unless the cable design allows pulling by a grip on the jacket. Any other method may put stress on the fibers and harm them. Cables that can be pulled by the jacket should use an approved cable grip, often called a “Kellems Grip.” These grips also usually are tied to the strength members.
Do not exceed the maximum pulling tension rating of the cable. Consult the cable manufacturer and suppliers of pulling equipment, conduit, innerduct and cable lubricants for guidelines on tension ratings and lubricant use.
Do not twist the cable. Tension on the cable and pulling ropes can cause twisting. Use a swivel pulling eye to connect the pull rope to the cable to prevent pulling tension and twisting forces on the cable.
Rather than spinning, roll the cable off the spool end to prevent putting a twist in the cable for every turn on the spool. When laying cable out for a long pull, use a figure 8 on the ground to prevent twisting. The figure 8 puts a half-twist in on one side of the 8 and takes it out on the other, preventing twists.
Do not exceed the cable bend radius. Fiber optic cable can be broken when kinked or bent too tightly, especially during pulling. If no specific recommendations are available from the cable manufacturer, the cable should not be pulled over a bend radius smaller than 20 times the cable diameter. After completion of the installation, the cable should not have any bend radius smaller than 10 times the cable diameter.
Fiber optic cables, like all communications cables, are sensitive to compressive or crushing loads. Cable ties, especially when tightened with an installation tool, may harm fiber optic cables, causing attenuation and potential fiber breakage. When used, cable ties should be hand tightened to be snug but loose enough to be moved along the cable by hand. The excess length of the tie should be cut off to prevent future tightening. Hook-and-loop fastener ties are preferred for fiber optic cables, as they cannot apply crush loads sufficient to harm the cable.
Conductive cables require proper grounding and bonding for applicable conductors. Although most fiber optic cables are not conductive, any metallic hardware used in fiber optic cabling systems (such as wall-mounted termination boxes, racks and patch panels) must be grounded. Grounding systems shall be designed as specified by the National Electrical Code and other applicable codes and standards.
As I said, one needs to use one’s judgment to properly install fiber optic cable. At every step, consider the consequences of your actions to minimize the potential harm to the cable and to leave an installation that perfectly exemplifies installing in a “neat and workmanlike manner.”
HAYES is a VDV writer and educator and the president of The Fiber Optic Association. Find him at www.JimHayes.com.