Requirements for Airflow Optical Cable Laying

Air-assisted installation, also known as blowing or jetting, uses compressed air to float optical fiber cables through ducts, enabling long-distance, low-friction installation.

Overview of Air-

Assisted InstallationAir-assisted installation is a modern technique for laying optical fiber cables in pre-installed ducts. It combines mechanical pushing with high-speed airflow to reduce friction and stress on the cable, allowing longer continuous runs compared to traditional pulling methods. This method is particularly effective in ducts with multiple bends, undulations, or long distances, and is widely used in urban and hard-to-reach areas.

Methods: Blowing vs JettingBlowing: Compressed air is injected into the duct, creating a drag force along the cable. The cable is pushed mechanically near the duct entrance, and the airflow keeps it "floating" inside the duct, minimizing contact with the duct walls. No reaction head is used; the pulling force is distributed along the cable length.

Jetting: A reaction head or "parachute" is attached to the cable end. Differential air pressure across the head generates a pulling force, assisting the cable through the duct. Jetting is often used interchangeably with blowing, but the key difference is the use of a reaction head.

Both methods rely on airflow to reduce sidewall pressure, preventing cable damage and allowing longer installation distances.

Equipment and Setup

Blowing machines: Equipped with traction rollers or a tractor mechanism to push the cable initially. Air compressors: Provide high-speed airflow to float the cable through the duct. Cable guides or bullets: Ensure smooth entry and prevent kinking; the bullet diameter should match the cable diameter.

Test benches: Used to determine maximum safe pushing force and prevent cable buckling or sheath damage.

Cable and Duct Considerations

Cable type: Standard optical fiber cables (uni-tube, multi-tube, armored, unarmored) and microduct cables are suitable. Cable stiffness: Stiffer cables perform better in straight ducts, while flexible cables navigate bends more effectively. Duct conditions: Smooth, continuous ducts with properly sealed joints improve installation success.

Temperature and humidity can affect polyethylene ducts, potentially causing deformation or increased friction.

Installation Performance

Typical single-device installations can achieve 1,500–2,100 meters (5,000–7,000 feet) under good conditions. Longer distances can be achieved using mid-assist devices along the duct. Air-assisted methods reduce labor, installation time, and material handling compared to manual pulling, especially for long or complex duct routes.

Best Practices

Conduct a crash test to determine safe pushing force before full installation. Ensure continuous inner-duct runs and check duct integrity to prevent installation failure. Monitor cable tension, bending radius, and crush limits to avoid damage during installation.

Use appropriate airflow and pushing force based on cable type, duct length, and route complexity. Air-assisted installation is a reliable, efficient, and safe method for deploying optical fiber networks, particularly in long or challenging duct routes, offering significant advantages over traditional pulling methods.