How to Choose the Right Conduit for Your Fiber Optic Installation

What is the role of Conduit for Fiber Optic cable installations?

Before we dive into the specifics of conduit selection, it's essential to understand the purpose of a conduit in a fiber optic installation. 

A conduit is a protective tube or channel that houses the fiber optic cables, shielding them from moisture, dust, physical stress, and other environmental factors. 

It also facilitates cable management and ease of maintenance.

With these assemblies we mention in this article, the widest point of your assembly will typically be the pulling eye during installation which is ¾. Installing your Pre-Terminated Assembly in too tight of a conduit or exerting pulling tension on your assembly could break it. 

Therefore, we recommend pre-lubricating your conduit, and selecting the correct conduit size to avoid any issues.

When it comes to choosing the right conduit for your fiber optic installation, several factors need to be considered:

Do I Need to Use Conduit for All Fiber Optic Cable Installations?

The necessity of using conduit depends on the installation environment. 

While indoor installations may not require conduit in some cases, outdoor, underground, underwater, or aerial installations almost always do. 

Here's a breakdown of when conduit is typically required:

Indoor Installations:

For indoor installations, conduit may be optional in controlled environments with minimal risk of cable damage. 

However, using conduit can still provide additional protection, especially in commercial or industrial settings where cables may be exposed to physical stress.

Underground Installations:

Underground installations typically demand conduit to protect the fiber optic cables from soil moisture, mechanical damage, and environmental changes. 

For example, an Indoor/Outdoor jacket that needs to be buried underground must be in a conduit. This type of fiber optic jacket is not suitable to be exposed underground, and will also not be protected from external factors like rodents or shovels. 

However, Outside Plant, also known as OSP fiber optic jackets, are suitable to be buried directly underground as the jacket material will be made with a polyethylene jacket. If the fiber is also armored, this provides the level of protection that a conduit would. 

Installing armored fiber through a conduit could increase your chances of breaking the fiber, so with that said conduit for an armored OSP fiber is not always necessary, but conduits help ensure the long-term integrity of the installation.

Underwater Installations:

When deploying fiber optic cables underwater, such as in marine or submarine applications, specialized underwater conduit is essential. 

This conduit is designed to withstand the unique challenges posed by submersion, including water pressure and marine life.

Aerial Installations:

Conduit in aerial installations, where cables are suspended on poles or towers, is another area where it may or may not make sense to use conduit. 

Aerial fiber that has an Outside Plant, also known as OSP jacket, will have protection from weather conditions and UV radiation. 

Typically this fiber comes in a figure eight configuration which has a wire messenger that can help deter rodents. 

Fiber that is being run on a tower  usually needs to be free from metal so a conduit can help to protect the fiber from external outdoor factors, however this fiber will still have a UV rated jacket and water blocking properties within the cable composition. 

Benefits of Fiber Optic Conduit

Using conduit for your fiber optic installation offers several benefits:

Protection

Conduit shields the cables from moisture, dirt, chemicals, and physical damage, ensuring the longevity and performance of the fiber optic cables.

Easy Maintenance: 

Conduit makes it easier to locate, access, and replace cables when necessary, reducing downtime during maintenance or upgrades.

Cable Management:

Conduit organizes and secures cables, preventing tangling and ensuring efficient cable routing.

Environmental Resistance: 

Conduit materials can be chosen to resist specific environmental challenges, such as UV radiation, chemicals, or extreme temperatures.

Regulatory Compliance: 

In some regions and industries, using conduit is a regulatory requirement to meet safety and performance standards.

What Size Conduit Should I Use for Different Types of Assemblies?

The size of conduit you should use depends on the type of fiber optic assembly and the number of cables it will house. 

This chart explains the size of conduit you need for the most common assemblies and installations.  Keep in mind that conduit size information in this tutorial is specific to our line of QuickTreX pre-terminated fiber optic assemblies.  

Understanding fill factor in conduit runs

“Fill factor” or conduit fill, states the maximum amount of space that the installed cables should occupy in a given size conduit, expressed as a percentage of the interior volume. 

For example, if we were planning to pull three cables into a conduit, the combined cross-sectional area of the three cables, must not exceed 40% of the conduit’s interior volume. Because the table does not specify high or low-voltage cable(s), it can apply to both.

Consider not only the cables that will be installed now, but the likelihood of having to add cables in the future.