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How To Install Outdoor Fiber Optic Cables In Underground Ducts And Innerducts

By: Colin Yao
Fiber ducts are usually made from HDPE (high-density polyethylene), PVC or other compound. They are usually in black or gray. Fiber innerduct is usually orange or yellow.

:: Why usually fiber ducts and innerducts are corrugated?

Fiber ducts and innerducts are corrugated to provide the following benefits:

1. Decreasing pulling tensions during installation

2. Very flexible and can be used in installation locations where many turns are involved

3. After installation, corrugated innerduct should be left for a day to allow the innerduct to retreat back into the duct through its corrugated spring action

:: The use of pulling tape

Fiber optic cable pulling tape is preinstalled in fiber duct and innerduct in the factory. This saves significant time during the installation process. Duct and innerduct can also be pre-lubricated in the factory, thus significantly reduces pulling tensions.

:: Never bend over its minimum bend radius

Just like fiber optic cable, fiber duct and innerduct also have a minimum bend radius spec. Never ever should the duct or innerduct be bent tighter than its minimum bend radius.

:: What is supported radius?

The supported radius is the minimum bend radius when the duct is bent around a supporting structure such as in another duct or on a reel.

:: What is unsupported radius?

The unsupported radius is the minimum bend radius when the duct has no supporting structure in the bend.

:: Benefits of using fiber duct

Fiber duct protects the fiber cable and also provides an opportunity for future cable access and expansion. Fiber optic cable can be pulling into existing duct. The duct should usually be oversized to allow future cables be pulled in.

:: Benefits of using fiber innerduct

Fiber innerduct provides protection for the fiber cable from being disturbed by other companies' cable installation operation. It also provides extra protection from the environment. Or fiber innerduct can be used in old duct installation.

:: Things to keep in mind

1. Install end plugs

After the fiber optic cable is installed into a duct or innerduct, end plugs should be installed to provide a water seal. No debris should be able to enter the duct or innerduct, and watertight should always be maintained for the duct or innerduct.

2. Duct and innerduct should be properly sized for future expansion possibility

As always, planning for future expansion is crucial for real successful projects. A maximum of 40% fill ratio is a good practice to follow. The duct size should be increased for long installation lengths with many turns. A larger duct can help to reduce cable-pulling tensions. Standard duct sizes vary from 3 to 8 inch ID and innerduct sizes vary from 0.75 to 2 inch.

:: The benefit of using duct lubricant

Duct lubricant can significantly reduce the cable's coefficient of friction, thus lessening the pulling tension during cable pulling process. This is especially important in long cable duct pulls and pulls with many turns.

Duct lubricant spillage should be cleaned up as soon as possible to prevent accident since it is very slippery. Manufactures' recommended procedure for cleaning lubricant provides good instruction on how to do the cleaning.

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About The Author, Colin Yao

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