Fiber optic cables are commonly installed indoor and outdoor for inside and outside plants in LANs, MANs and WANs. This article describes some of the common fiber cable installation methods.
:: Indoor Fiber Optic Cable Installation
Indoor fiber cables should be placed in conduits or trays. Most fiber cables are non-conductive so they can be placed alongside high voltage cables without any special insulation.
cable installation must meet the NEC and local building code. Properly fiber rated fiber cables can use the same cable tray or raceway with conductors for electric light, power or Class 1 circuits 600V or less.
:: Fiber Cable Installation in Trays and Ducts
The main concern for planning indoor fiber cable routes is to avoid any cutting edges and sharp bends. This includes corners and exit slots of trays.
The critical consideration when planning cable duct and trays is the bending radius. All bends must have smooth curves. When a fiber cable is pulled into a conduit or cable tray, the conduit’s bending radius must be larger than the cable’s minimum bending radius for loaded conditions.
Cables in ducts and trays are not subjected to tensile forces. But for vertical runs, this must be carefully designed to minimize the tensile force applied to the vertical run fiber cables. Long vertical runs must be clamped at intermediate points to prevent excessive tensile loading on the fiber cable. The clamping force should be applied over as long a length of the fiber optic cable as practical.
If frequent clamping is not possible, cable hangers can be used at the top of the vertical rises and at intermediate locations along the vertical rises. A popular choice for this situation is the mesh grip or split mesh grip hanger as shown below.
Pull boxes are placed near bends and in long straight spans to break up long conduit runs for easier and lower tension pulls. You should install one pull box after every second 90° bend and in long conduit runs.
When pulling fiber cables out of pull boxes, ensure that the cable’s minimum bending radius is not compromised. Be extremely careful of the sharp corners of the pull box since that can easily damage the fiber cables.
:: Pulling Fiber Optic Cable
The pulling process for fiber cable installation is inherited from copper cabling process. They share many the same concepts and tools. But there are special considerations for fiber cables: minimum bend radius must be preserved, only smaller pulling forces are allowed and fiber connectors installed on the cable must be carefully protected.
A pull tape or cable net is attached to the optical cable in such a way that the pulling force is only applied to the Kevlar strength members in the cable jacket. cable netting is required to prevent damaging fiber connectors.
A popular method for attaching fiber cable is fiber optic cable grip. The grip is stretched and wrapped around the fiber cable, a tape layer is tightly wrapped on the outside again to provide a firm grip on the cable.
During an installation, the pulling force should be constantly monitored by a mechanical gauge. This can be done by using a line tensiometer, a breakaway or a dynamometer.