How to erect optical cables overhead

Overhead optical cables are installed by selecting appropriate poles, using proper cable types, ensuring correct tension and sag, and following safety and environmental standards.

Preparation and Planning

Before installation, conduct a route survey to identify obstacles, terrain, and existing infrastructure. Obtain permits from local authorities and coordinate with utility companies if sharing poles with power lines. Ensure all materials, tools, and a skilled construction team are ready, as fiber optic cables are sensitive to bending and tension, and improper handling can cause signal loss or breakage.

Pole Selection and Spacing

Pole height typically ranges from 7m to 12m depending on terrain and obstacles, with reinforced poles for extreme environments. Pole spacing is generally 25–40m in urban areas, 40–50m in suburban/rural areas, and up to 67m for reinforced structures. Poles must be vertically aligned, with corner poles slightly tilted toward tension wires, and terminal poles tilted 10–20 cm toward the cable side.

Cable Types and SupportSelf-supporting cables (ADSS) do not require additional support wires and are suitable for long spans and areas near power lines. Messenger-supported cables use a steel wire for support, providing extra tensile strength and stability in windy or icy conditions. Ensure the bending radius is at least 20 times the cable diameter to prevent microbending losses.

Installation Methods

Moving reel method: The cable is pulled from a moving reel along the route. Stationary reel method: The cable is unwound from a fixed reel at each segment. Use galvanized steel stranded wire for hanging if required, and maintain a minimum ground clearance of 5m and horizontal/vertical distance from power lines of at least 2m.

Tensioning and Sag

Apply tension carefully, typically 150–200 kg, to avoid overstressing the fiber. Adjust sag according to span length and environmental conditions, ensuring the cable does not interfere with roads or structures.

Grounding and Protection

Ground all metallic components, including messenger wires and brackets, to protect against lightning and electrical hazards. Use protective sleeves at intersections with other utilities to prevent abrasion and damage. Polyethylene jackets with carbon black are recommended for UV protection.

Splicing and Slack Management

Leave slack at intervals (5–10% of cable length) for splicing and future maintenance. Plan splice points with access for vehicles and equipment, ensuring minimal signal loss during fusion splicing.

Final Checks

Verify pole alignment, cable tension, sag, and grounding. Conduct optical testing to ensure minimal signal loss and compliance with design specifications. Document the installation for future maintenance and troubleshooting.

By following these steps, overhead optical cables can be safely and efficiently erected, ensuring long-term performance and reliability in diverse environments.