Requirements for optical cable laying using the air blowing method

Air-blown optical cable installation requires proper cable selection, duct sizing, mechanical pushing, and controlled compressed air to ensure safe and efficient deployment.

Cable and Duct Requirements

• Cable Types: Standard optical fiber cables (uni-tube, multi-tube, armored, unarmored) and microduct cables can be installed using this method . Cables should have low friction outer jackets to reduce resistance inside the duct .
• Cable Stiffness: Stiffer cables are preferred for straight ducts and longer distances, while more flexible cables are suitable for routes with multiple bends .
• Duct Size: The duct should be slightly larger than the cable to allow smooth airflow and reduce friction. The Duct Fill Ratio (DFR) should ideally be between 30–80% depending on calculation method .
• Microducts: For microduct installations, cables with polyethylene (PE) sheaths and optimal stiffness are recommended to prevent buckling and facilitate navigation through bends .

Equipment and Installation Procedure

• Blowing Device: A tractor mechanism with traction rollers is used to push the cable a few hundred meters into the duct before introducing compressed air .
• Compressed Air: Air is injected to “float” the cable, minimizing sidewall pressure and friction. Air pressure should be controlled to avoid cable damage, using the minimum required to move the cable .
• Blowing Head: The cable is attached to a blowing head or piston that seals the duct and allows air to push the cable forward. For larger ducts, piston-assisted blowing is preferred .
• Crash Test: Before full installation, a crash test is performed by pushing the cable into a sealed duct section to determine the maximum safe pushing force and prevent jacket damage or buckling .

Environmental and Operational Considerations

• Temperature: Avoid installing cables in extremely cold conditions, as the jacket may become brittle and more prone to damage .
• Route Planning: Straight trajectories allow longer blowing distances, while multiple bends or undulations may require mid-assist devices to extend cable reach .
• Lubrication: Optional low-friction lubricants can be applied to further reduce resistance and facilitate cable movement .

Performance and Distance

• Typical Lengths: Single air-assisted devices can install 1,500–2,100 meters of cable under optimal conditions. Longer distances can be achieved using mid-assist devices along the route .
• Force Distribution: In blowing, the pulling force is distributed along the cable length due to air drag, unlike jetting which uses a reaction head . By following these requirements—selecting the right cable, ensuring proper duct sizing, using controlled air pressure, and performing pre-installation tests—optical fiber cables can be efficiently and safely installed using the air-blowing method.