FAQ on Fiber Optic Cable Handling and Installation

Published: 20th May 2008
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:: 1. What is the difference between copper cable and fiber optic cable?

Even though fiber optic cables may look like traditional copper cables, we should always keep in mind that inside fiber cables are fragile glass fibers which can be broken easily if not properly handled.

:: 2. What are the most important things to obey in fiber cable installation?

During any fiber optic cable installation project, we must keep two very important things in mind: First, never over-bend the fiber cable over its minimum bend radius. Second, never pull over the cable manufacturer's cable pulling tension specification.

:: 3. What is a Minimum Bend Radius?

Fiber cables all have a minimum bend radius specification by the manufacturers. This the minimum curve radius while bending the fiber cable in either installation process or after the installation in its final resting position. You can make larger curves but never smaller than specified.

:: 4. What is Fiber Cable Loaded Minimum Bend Radius?

Loaded minimum bend radius is the fiber cable bend radius specification during a cable pull as in the installation process. The cable must not bend tighter than its loaded minimum bend radius at any time during the installation process. Loaded minimum bend radius is larger than unloaded minimum bend radius as explained below.

:: 5. What is Fiber Cable Unloaded Minimum Bend Radius?

Unloaded minimum bend radius is the fiber bending radius specification in the cable's final resting position after installation. That is when the cable is not under any tension. Unloaded minimum bend radius is smaller than loaded minimum bend radius. Often, this spec is determined by a simple multiplication such as 15~25 X OD (fiber cable outside diameter).

:: 6. What is Fiber's Minimum Bend Radius?

Fiber optic cables are composed of individual fibers (strands). Individual fibers also have a minimum bend radius specification, which is usually 2~3 cm and is much smaller than jacket cables.

:: 7. What will happen if a fiber cable is bent smaller than its minimum bend radius?

Bending a fiber cable over its minimum bend radius is one of biggest factors in fiber damaging in fiber cable installation projects. This practice can either break the inside fibers or increase fiber attenuation (fiber power loss) over the manufacturer's specification. Even if the inside fibers are already broken, you may not see any physical damage to the outside jacket at all. The consequence is, you have to replace the whole section or even the entire length of cable. As a good practice, all fibers need to be thoroughly tested after cable installation.

:: 8. What is Pulling Tension?

Pulling tension is the force placed on per square unit of fiber cable cross section. Maximum pulling tensions during fiber cable installation are specified by cable manufacturers and should not be exceeded at any time. Most tensile load on a cable will occur in a vertical installation and is caused by the cable's own weight.

:: 9. Other Fiber Optic Cable Installation Tips

a. The cable should be pulled by hand as much as possible
b. Pulling tension should always be monitored when using mechanical pulling techniques
c. Cable should be pulled in a steady, continuous motion and never jerked
d. Never push a fiber optic cable
e. Using the minimum possible tension while pulling fiber cables


Colin Yao is an expert on fiber optic technologies and products. Learn even more about multimode fiber optic cable, fiber optic ribbon cable, ribbon fiber on Fiber Optics For Sale Co. web site.

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