Requirements for laying optical cables using the air-blowing method

Air-blown fiber optic cable installation requires proper duct preparation, suitable cable selection, controlled air pressure, and adherence to bending and fill ratio specifications to ensure efficient and safe deployment.

Planning and Preparation

Before installation, the cable route must be carefully planned, considering existing infrastructure, obstacles, and access points. The pathway should be cleared of debris, moisture, and sharp edges to prevent cable damage during installation. All necessary equipment, including blowing machines, compressed air sources, fiber cables, connectors, and lubricants, should be prepared in advance.

Cable and Duct Requirements

Cable Types: Standard optical fiber cables (uni-tube, multi-tube, armored, unarmored) and microduct cables are suitable for air-blowing installation. Cable Stiffness: Stiffer cables perform better in straight ducts and undulations, while flexible cables are preferable for routes with multiple bends. Duct Fill Ratio: Optimal cable-to-duct fill ratio ranges from 50% to 80% to minimize friction and prevent helical waves inside the duct.

Minimum Bend Radius: The radius of conduit bends, cable guides, sheaves, and capstans must be equal to or greater than the cable's minimum bending radius to avoid fiber damage.

Air Pressure and Blowing Equipment

Air Pressure: Typical air pressure for cable-blowing machines ranges from 10 to 15 bars, depending on duct length, cable diameter, and equipment specifications. Blowing Mechanism: The cable is initially pushed a few hundred meters using a tractor mechanism with traction rollers. Compressed air is then introduced to float the cable inside the duct, reducing friction and sidewall pressure.

Cable End Attachment: A “bullet” or blowing head, matching the cable diameter, is attached to the cable end to facilitate smooth air-assisted movement.

Installation Considerations

Distance: Under optimal conditions, air-blown cables can be installed continuously over 1,000 to 2,000 meters. Longer distances may require mid-assist devices to maintain air flow and pushing force. Mechanical Pushing Force: The maximum pushing force should be determined through on-site testing to prevent cable buckling, especially for smaller diameter cables.

Cable Preparation: Strip the outer sheath and buffer tubes as required, exposing fibers for connection while ensuring the cable meets network specifications.

Safety and Best Practices

Avoid sharp bends and obstructions along the duct route. Monitor air pressure and pushing force continuously to prevent cable damage. Ensure proper lubrication if required to reduce friction.

Follow manufacturer guidelines for cable handling, minimum bend radius, and maximum tensile stress. By adhering to these technical requirements, air-blown fiber optic cable installation can achieve efficient, long-distance deployment with minimal risk of cable damage, reduced labor, and flexibility for future network expansions.