How to Choose the Right Conduit for Your Fiber Optic Installation

How to Choose the Right Conduit for Your Fiber Optic Installation

Fiber optic cables have revolutionized the way we transmit data, offering high-speed connectivity and reliable performance. Whether you’re setting up a network in your home or installing fiber optic cables for a large-scale project, one crucial factor to consider is the conduit. The conduit protects the fragile fiber optic cables from environmental factors and physical damage, ensuring their longevity and optimal performance.

In this comprehensive guide, we will walk you through the process of choosing 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 is 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. Conduit 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 Condit for All Fiber Optic Cable Installations?

The necessity of using cable depends on the installation environment. While indoor installations may not require conduit in some cases, outdoor, underground, underwater, or aerial installations almost always do.

Indoor Installations

For indoor installations, conduit may be an option 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, and 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

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 OSP 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.


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.

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

How to go About Choosing a Conduit Size

Choosing the right conduit size and properly applying lubricant are crucial for a smooth installation of pre-terminated fiber-optic assemblies. Factors such as distance, number of cables, and friction should be considered. You may also need to consider using an oversized conduit to reduce friction during installation. Choosing an oversized conduit with a large bend radius can help reduce friction and make installation easier for fiber optic cabling. For example, using a two-inch conduit size can reduce friction and make each pole shorter by replacing conduit bends with pull boxes.

How to Pre-lubricate Conduit for Pulling Fiber Optic Cabling

Pre-lubricating a conduit can reduce the required pulling force by 40% of more, making the process of pulling fiber optic cabling easier and more efficient. The process of lubrication involves pulling the string in both directions, attaching a rag with a quarter inch pulling rope, and repeating the lubrication process. Lubricating the conduit multiple times is recommended for long and challenging fiber optic cable pulls, indicating the importance of ensuring smooth and efficient installation.

How is Fiber Optic Conduit Installed

Installing fiber optic conduit involves several key steps.

Plan the Route

You should always create a detailed installation plan. Determine the path the conduit will follow, considering factors like distance, obstacles, and access points.

Prepare the Trench or Duct

If you are burying the conduit underground, dig a trench of the appropriate depth, taking care to avoid damaging existing utilities. For indoor installations, create an open channel or use existing cable trays or raceways.

Attach Conduit Supports

Install conduit supports, such as hangers, straps, or brackets to secure the conduit along the chosen route.

Pull or Place Cables

Depending on the installation type, pull or place the fiber optic cables into the conduit. Use cable lubricants to reduce friction and avoid cable damage.

Seal and Terminate

Seal the conduit ends and junction points to prevent moisture and debris ingress. Terminate the cables at their destination, ensuring proper connectors and splices.

Test and Verify

Conduct thorough testing to verify the integrity and performance of the fiber optic cables. Ensure there are no bends or kinks exceeding the cable’s bend radius.

Label and Document

Label each conduit and cable for easy identification and maintenance. Create comprehensive documentation of the installation, including cable types, routes, and splice locations.

AerosUSA Products



Galvanized and stainless-steel conduits providing high flexibility, stretch resistance and lateral compression resistance. These conduits are IP40 and operate most effectively against the risks of abrasion and impact.


Flexible metal conduits are designed to help protect against hot and cold temperatures, liquids, abrasions, gases and more. Made from a helix of stainless steel, fiber glass braiding and silicone rubber sheathing, these specialized conduits provide superior flexibility. Commonly used for endoscopes in the medical field.


A special protective conduit helix for the sensor technology and beam wave guide technology. These products are stainless steel and operate in the temperature range of -200°C up to 600°F (-200°F to 1,112°F). Due to their durability and resistance to damage, these conduits can improve the longevity of your fiber optic systems.


IP 68 rated conduits created from galvanized steel with PVC sheathing. Designed to keep cables and wires safe and protected, these fiber cable protection tubes are weatherproof and resistant to seawater, acids, and oils. They provide high flexibility, stretch resistance, compression resistance and are non-flame propagating.


What is the conduit bend radius?

The conduit bend radius refers to the minimum allowable curvature that a fiber optic cable can safely bend around when installed within a conduit. Exceeding the bend radius can cause signal loss or damage to the cable. The bend radius varies depending on the cable type and manufacturer but is typically specified in the cable’s datasheet. It is essential to follow these guidelines to maintain cable performance and prevent signal attenuation.

What is the Conduit Fill Ration?

The conduit fill ratio is the percentage of the conduit’s cross-sectional area occupied by cables. Exceeding the recommended fill ration can lead to overheating and signal degradation.

Reviewed for accuracy by: George Sims.
George Sims is an engineering and service-oriented leader in Cable Protection and Cable Management Products. Focus is on 100% commitment to customer satisfaction. AerosUSA is a small, agile, independent company whose focus is on our customers.