Procedure for Laying Optical Cables in Ducts

Optical cables in ducts are installed using careful preparation, duct conditioning, and either pulling or blowing methods to ensure minimal stress and damage to the fibers. 1.

Planning and Preparation

Before installation, conduct a route survey to identify manholes, duct paths, and potential obstacles. Determine the number of ducts, their diameters, and the type of cable to be installed, considering future network expansion and maximum cable bend radius requirements. Prepare a security and safety plan, including signage, barricades, and authorization from relevant authorities.

2.

Duct Conditioning

Clean and inspect ducts to remove debris, moisture, or toxic gases. Ensure ducts are free of sharp edges and obstructions. For long runs, consider duct lubrication to reduce friction during cable installation.

Identify locations for cable loops or slack storage in manholes to accommodate thermal expansion and maintenance. 3.

Cable Handling

Drum Conditioning: Place cable drums on rotatable stands to allow smooth unrolling. Use a figure-eight configuration for lengths over 30 meters to prevent twisting or kinking. Bend Radius: Respect the cable's minimum bend radius during installation, typically 15 times the cable diameter for working bends.

Tensile Load: Do not exceed the maximum pulling tension specified in the cable datasheet to avoid fiber strain or damage. 4.

Installation Methods

Pulling Method

Attach a pulling rope or swivel to the cable end. Use rollers or pull wheels to guide the cable through bends and manholes. Maintain a steady, controlled pulling speed to prevent excessive tension.

Monitor the cable for kinks, twists, or damage during the process. Blowing (Jetting) MethodPush the cable a few meters into the duct using a tractor mechanism or rollers. Inject compressed air at high speed to float the cable along the duct, reducing friction and mechanical stress.

Perform a crash test on a short duct section to determine the maximum safe pushing force and prevent buckling or sheath damage. Blowing is particularly effective for long ducts with multiple bends and for microduct cables. 5.

Post-

Installation Checks

Inspect the cable for physical damage and ensure it is properly seated in loops or slack areas. Record the cable route, duct numbers, and loop locations for future maintenance. Perform optical testing (OTDR or power loss measurements) to verify signal integrity and detect any installation-induced faults.

6.

Documentation and Safety

Maintain detailed records of the installation, including tension logs, duct conditions, and test results. Ensure all work areas are cleared, and safety measures are removed only after confirming the cable is secure. By following these steps, optical fiber cables can be installed efficiently in ducts while minimizing the risk of damage, ensuring long-term reliability, and allowing for future network expansion.