Laying optical cables in indoor vertical shafts

Use OFNR-rated riser cables with proper mechanical support, fireproofing, and careful handling to safely install optical fibers in vertical shafts.

Cable Selection

For indoor vertical shafts, OFNR (Optical Fiber Nonconductive Riser) cables are recommended. These cables are specifically designed for vertical riser applications and comply with the National Electric Code (NEC 2023) for fire safety in multi-story buildings . Backbone cables with higher tensile ratings are preferred for vertical runs because they must support their own weight over multiple floors . Avoid using interconnect or light-duty cables in vertical shafts, as they are not designed for long vertical spans.

Mechanical Support and Conduit

Cables should be firmly secured along the shaft using nylon ties, steel clips, or cable trays at regular intervals to prevent sagging or slipping . In deep shafts or high-rise buildings, consider using conduit pipes capable of withstanding tensile forces and potential impacts from equipment hoisting . Circular shafts are ideal for structural stability, and conduit materials like Pexgol or flame-retardant PVC can handle both mechanical stress and temperature variations during installation .

Fire and Safety Considerations

Fireproofing is critical in vertical shafts. Seal all pipe penetrations with fire-resistant materials to prevent smoke and flame propagation between floors . Ensure cables are riser-rated and comply with NEC fire codes. Installers should wear safety gear including helmets, gloves, and eye protection, and avoid stepping on cables or equipment while working at height . Use ladders or scaffolding safely and keep hands free when ascending or descending.

Handling and Installation Practices

• Keep the protective covering on cable reels until installation to prevent damage .
• Inspect reels for protrusions or broken flanges before unrolling.
• Avoid excessive pulling, bending, or crushing forces, as these can degrade optical performance .
• Use cable lubricants if necessary, but clean up spills to prevent slips .
• Reserve extra cable length according to design requirements to allow for proper routing and slack .

Testing and Verification

Before finalizing the installation, test the cable for optical continuity using an OTDR or similar device to ensure no damage occurred during installation . Pre-connectorized sections should be handled carefully to avoid replacing entire sections due to minor damage.

Summary

Proper installation of optical cables in indoor vertical shafts requires riser-rated cables, secure mechanical support, fireproofing, careful handling, and adherence to safety standards. Following these guidelines ensures reliable performance, compliance with fire codes, and long-term durability of the fiber network .