Laying optical cables at high altitudes

High-altitude optical cables are typically installed as aerial or overhead lines using specialized self-supporting or messenger-supported cables, designed to withstand extreme environmental conditions and mechanical stresses.

Cable Types and Selection

High-altitude installations often use All-Dielectric Self-Supporting (ADSS) cables or Optical Fiber Composite Overhead Ground Wire (OPGW). ADSS cables are non-metallic, allowing installation near high-voltage lines without electrical conduction, while OPGW combines optical fibers with a grounded conductor for high-voltage transmission systems, providing both communication and lightning protection . Cable selection depends on span length, environmental conditions, and mechanical load requirements.

Installation Requirements

• Pole and Tower Spacing: In extreme environments, poles or lattice towers may be spaced up to 67 meters, with reinforced steel structures to handle tension and wind loads .
• Tensile Strength: Cables must withstand high mechanical stress, with ADSS cables rated from 1,500N for short spans to 12,000N for long spans .
• Temperature and Environmental Resistance: Outdoor cables are designed for -40°C to +80°C and must resist ice, wind, and UV exposure. Jackets often include carbon black in polyethylene to prevent UV degradation .
• Sag and Tension Management: Proper sag is critical; cables must be stretched correctly during installation to account for elongation under maximum load .

Installation Process

1. Route Survey and Design: Survey the terrain, identify pole locations, and plan splice points and slack storage .
2. Permits and Coordination: Obtain permits for pole use and coordinate with local authorities, especially in mountainous or high-altitude regions .
3. Pole Preparation: Existing poles may need reinforcement or renovation to meet mechanical requirements. Hanging wires or steel strands are installed to support the cable .
4. Cable Erection: Cables are either lashed to messenger wires or self-supported. Hooks and clamps are spaced evenly, typically 50 cm apart, with minimal deviation .
5. Safety Measures: Workers must use personal protective equipment, maintain 3-point contact on ladders, and follow strict safety protocols due to working at height and near electrical lines .

Advantages of High-Altitude Aerial Installation

• Cost Efficiency: Avoids trenching and excavation, reducing costs by 30–50% .
• Rapid Deployment: Installation is 2–3 times faster than underground methods .
• Flexibility: Adapts to uneven or rocky terrain without extensive groundwork .

Considerations

High-altitude installations face higher failure risks due to ice, wind, and natural disasters. Reinforced structures, proper tensioning, and durable cable materials are essential to maintain long-term reliability . By following these standards and using appropriate cable types, high-altitude optical networks can achieve robust performance, safety, and cost-effective deployment in challenging terrains.