Flame-retardant optical cables maintain optical integrity under high temperatures, with attenuation changes typically below 1 dB during fire exposure.

Fire Performance and Coefficients

Flame-retardant optical cables are designed to resist fire and maintain signal transmission. Key performance metrics include:

• Temperature Index: Many cables withstand temperatures up to 370°C for ceramic sheathing materials according to EN ISO 4589 .
• Attenuation Change: Under fire conditions, the maximum change in optical fiber attenuation is typically 0.16 dB for 90 minutes at 750°C, and up to 0.78 dB under mechanical shock at 950°C .
• Flame Retardancy Standards: These cables comply with IEC60332-1-2 for single cable flammability and IEC60332-3-24 for multiple cable flammability . They also meet BS6387 CWZ for fire, water, and mechanical shock conditions .
• Continuous Operation: Fire-resistant cables, such as those certified to FE180 or CPR B2ca, ensure continuous data transmission during fire, protecting critical communication lines .

Material and Design Considerations

• Halogen-Free Sheath: Reduces toxic gas emission during fire .
• Reinforced Structure: Loose tubes around a central FRP strength member provide mechanical durability and bending resistance .
• Optical Integrity: Light transmittance remains above 68% even under fire conditions .

Standards and Certification

Flame-retardant optical cables are tested and certified by Nationally Recognized Testing Laboratories (NRTL) to ensure compliance with NEC, UL, CSA, and other safety standards . European cables often follow CPR B2ca classification, indicating very high fire performance with low smoke and zero halogen emissions .

Summary

The "coefficient" in the context of flame-retardant optical cables generally refers to attenuation change under fire, temperature index, and flammability ratings. These cables are engineered to maintain signal integrity, mechanical durability, and safety during extreme fire conditions, making them suitable for tunnels, data centers, hospitals, and other critical infrastructure .