Vertical shaft fiber optic cable installation

Fiber optic cables in vertical shafts are typically installed using durable conduit pipes, careful tension management, and controlled bending techniques to prevent damage.

Conduit Selection and Preparation

For deep vertical shafts, Pexgol pipes or similar high-strength conduits are often used to house fiber optic cables. These pipes can withstand high tensile forces, impact, and temperature variations, making them suitable for shafts hundreds of meters deep. Pipes are usually supplied in long coils to minimize joints, reducing installation time and risk of cable damage.

Mechanical connectors or supports are used to secure the conduit above the shaft before lowering.

Cable Handling and Pulling

Fiber optic cables are sensitive to tension, bending, and crushing forces. The maximum pulling tension must be respected according to the cable specification sheet, typically around 2,700 Newtons for stranded loose tube cables. During installation, cables should be unreeled in a figure-eight pattern to prevent twisting and kinking, with loops sized according to cable stiffness, commonly 2–4 meters for surface handling.

Sharp bends and abrupt directional changes must be avoided to maintain the minimum bend radius specified by the manufacturer. Installation ProcedurePre-Installation Checks: Inspect the shaft and conduit for sharp edges, debris, or obstacles that could damage the cable. Ensure the work area is properly signaled and safe for personnel.

Conduit Placement: Lower the conduit into the shaft, securing it at the top with mechanical connectors. For very deep shafts, the conduit may be embedded in concrete or supported along the shaft walls. Cable Feeding: Pull the fiber optic cable through the conduit slowly, maintaining tension within safe limits.

Use rollers or guides to prevent abrasion and maintain smooth curvature. Monitoring: Continuously monitor the cable for signs of stress, kinking, or sheath damage. Protective sheathing should remain in place until the cable is fully installed.

Post-

Installation: Once the cable is in place, perform inspections and tests to ensure integrity and signal performance. Secure the cable at both ends and provide strain relief as needed.

Safety and Environmental Considerations

Avoid exposing the cable to extreme temperatures beyond its rated limits. Ensure personnel follow safety protocols for working in confined vertical spaces. Use protective measures if the shaft contains abrasive or chemical materials that could degrade the cable sheath.

By following these methods, fiber optic cables can be safely and efficiently installed in vertical shafts, maintaining performance and longevity while minimizing the risk of mechanical damage.