Flame-retardant structure of butterfly-shaped optical cable

A flame-retardant butterfly-shaped optical cable features a multi-layered design with inner and outer sheaths, heat insulation, reinforcing members, and halogen-free protective layers to ensure fire resistance, mechanical strength, and environmental safety.

Core Structure

The butterfly-shaped optical cable is named for its cross-sectional shape resembling a butterfly, which allows it to integrate the characteristics of indoor soft cables and self-supporting cables . Its structure typically includes:

• Inner Sheath: Encases the optical fibers and provides the first layer of protection.
• Wrapping Layer: Surrounds the inner sheath to enhance mechanical stability.
• Second Sheath: Often an embossed aluminum sheath applied via argon arc welding, maintaining bending capability and mechanical integrity while contributing to flame retardancy .
• Heat Insulation Layer: Protects the fibers from high temperatures during fire exposure.
• First Sheath: The outermost layer, providing additional protection and flame resistance.

Reinforcement and Fiber Arrangement

• Optical Fibers: Usually G657.A type fibers are placed centrally within the sheath .
• Strengthening Members: Non-metallic (FRP) or steel wire members are positioned on both sides of the fibers to resist compression and tensile forces .
• Loose Tube or Micro-Bundle Design: Fibers are housed in loose tubes filled with fiber paste to prevent damage and maintain signal integrity under stress .

Flame-Retardant Materials

• Halogen-Free Sheaths: Materials like polypropylene carbonate (PPC) and sodium polyacrylate are used to avoid toxic gas release during combustion .
• Ceramic or Mica Tapes: Some designs incorporate ceramic fiber tapes or synthetic mica layers to enhance fire resistance and thermal insulation .
• Low Smoke Zero Halogen (LSZH) Outer Sheath: Reduces smoke and toxic gas emission in case of fire, improving safety in indoor environments .

Functional Advantages

• Flame Retardancy: The combination of halogen-free materials, heat insulation, and metallic or ceramic layers ensures the cable resists ignition and slows fire propagation .
• Mechanical Strength: Reinforcing members and embossed aluminum sheaths maintain bending capability and tensile strength, preventing fiber breakage under stress .
• Environmental Safety: Halogen-free and low-smoke materials reduce toxic emissions, making the cable suitable for indoor installations like intelligent buildings, campus networks, and FTTX deployments .

Summary

The flame-retardant butterfly-shaped optical cable achieves high fire safety, mechanical reliability, and environmental friendliness through a carefully engineered multi-layer structure. Key elements include inner and outer sheaths, heat insulation, reinforcing members, and halogen-free protective layers, making it ideal for modern network applications where both safety and performance are critical .