Installing fiber optic cable in conduit requires careful planning and execution to avoid damage to the sensitive fibers. The primary methods are pulling by hand or using a capstan.
Preparing the Conduit
- Ensure the conduit is clean and clear: Before you begin, inspect the conduit for any debris, sharp edges, or obstructions that could damage the cable during installation. Use a conduit brush or vacuum to clean the inside thoroughly.
- Lubricate the conduit: Apply a fiber-optic-specific lubricant to the inside of the conduit to reduce friction. Use a lubricant that is compatible with the cable jacket material. Avoid petroleum-based lubricants, as they can damage some cable types.
- Plan the route: Map out the entire conduit run, noting any bends or changes in elevation. Sharp bends increase friction and pulling tension. Consider using sweeps (gradual bends) instead of elbows (sharp bends) to minimize stress on the cable.
Pulling Methods
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Manual Pulling:
- Ideal for short, straight runs: This method is suitable for shorter distances and conduits with few bends.
- Use a pulling grip: Attach a pulling grip (also known as a basket grip) to the end of the fiber optic cable. This grip distributes the pulling force evenly across the cable jacket, preventing damage.
- Hand-over-hand technique: Pull the cable slowly and steadily, avoiding sudden jerks or excessive force. It's helpful to have multiple people pulling along the route to distribute the effort.
- Monitor pulling tension: Keep a close eye on the pulling tension. Exceeding the cable's maximum pulling tension can damage the fibers.
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Capstan Pulling:
- For longer or more complex runs: A capstan (a rotating drum) provides mechanical advantage for pulling the cable through longer or more complex conduit runs.
- Use a dynamometer: A dynamometer measures the pulling tension. It is crucial to stay within the cable's maximum pulling tension rating.
- Capstan Diameter: Ensure the capstan diameter meets or exceeds the minimum bending radius of the fiber optic cable under the installed tensile load.
- Controlled Speed: Maintain a slow and consistent pulling speed to prevent stress and potential damage to the cable.
Key Considerations
- Minimum Bending Radius: Adhere strictly to the manufacturer's specified minimum bending radius of the fiber optic cable. Exceeding this radius can cause signal loss or permanent damage.
- Pulling Tension: Never exceed the maximum pulling tension specified by the cable manufacturer. Using a dynamometer is crucial for monitoring tension during capstan pulling.
- Cable Lubricant: Use a fiber-optic-specific lubricant to reduce friction and prevent damage to the cable jacket.
- Communication: If multiple people are involved in the pulling process, establish clear communication to ensure a coordinated effort.
Post-Installation
- Test the cable: After installation, thoroughly test the fiber optic cable to ensure proper functionality and signal integrity.
- Document the route: Keep a detailed record of the conduit route, including cable type, pulling tension, and any splices or connections.
- Properly terminate: Ensure the fiber optic cable is properly terminated with appropriate connectors.
By following these steps and taking precautions, you can successfully install fiber optic cable in conduit while minimizing the risk of damage.
