Understanding Basic Terms in Indoor Fiber Optic Cable Installation
By Colin Yao
Fiber optic cables are exposed to electrical, mechanical, chemical and environmental
elements, so proper installation is critical for the long-term stability and survival of
Cable installation must also meet the NEC(National Electric Code) and local building
codes. NEC indicates that fiber optic cables can be placed in the same raceway, cable tray
or enclosure with CATV, telephone, communication circuits and Class 2 and 3 remote control
Note that you should never put the fiber optic cable in the same enclosure that houses
What are conduits?
Conduit is a tube or trough for protecting electrical or communication wires and cables.
It may be a solid or flexible tube in which cables are run. They house and protect the
fiber optic cables as well as any other type of data or communication transmission line.
Underground conduits are also called ducts and consist of one or more conduits spaced
closely together. They are often buried directly in the ground in concrete casing. Duct
lines terminate in underground vaults called manholes. Conduits are made of fiber, PVC, PE
and other materials.
Above ground conduits are made of metal or nonmetal materials. They can be used in
exposed or concealed locations aboveground.
Characteristics of a good conduit installation
1.Good mechanical properties to withstand the forces imposed by cable installations
2.Observes fiber optic cables minimum bending radius
3.No sharp edges or bends touches the fiber optic cables throughout the route
4.Meets current and future expansion requirements
What are cable trays?
A cable tray is an assembly of units made of metal or other noncombustible materials
that form a continuous, rigid support for fiber cables. Cable trays are used throughout
the industry and they greatly simplify the installation of fiber optic cables.
Cable trays come in several different types including ladder type, trough type, channel
type and solid-bottom type.
Ladder type cable tray is a metal structure consisting of two longitudinal side rails
connected by individual transverse members. The transverse members provide the support for
Trough type cable tray is also a metal structure. It consists of a ventilated bottom
and has closely spaced supports within integral or separate longitudinal side rails.
Channel type cable tray consists of a one-piece ventilated or solid-bottom channel section.
Solid-bottom type cable tray is a metal structure that has no openings in the bottom.
Integral or separate longitudinal side rails provide the support for the fiber cables.
What are pull boxes?
Pull boxes are used to break up long conduit lengths for easier and lower tension cable pulls.
Pull boxes are usually placed near conduit bends and in long straight runs. You should
use at least one pull box after every second 90° bend and in long conduit spans.
When pulling cable out of pull boxes, ensure that the cable's minimum bend radius is
always observed. Cable pulled through a corner pull box should first be pulled into a loop
since the sharp corner of the pull box can easily damage the cable and the fibers.
Colin Yao is an expert on fiber optic communication technologies and products. Learn more about
aerial fiber cable and
optic cable aerial
on Fiber Optics For Sale Co. web site.
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