Fiber optic cable sheath spacing

Fiber optic cable sheaths vary by application, typically using materials like PE, LSZH, or AT, with dimensions and thicknesses designed for mechanical protection, environmental resistance, and installation requirements.

Sheath Materials

• PE (Polyethylene): Common for outdoor and direct burial cables; UV resistant and durable against moisture and chemicals .
• LSZH (Low Smoke Zero Halogen): Used in indoor or plenum applications to reduce toxic fumes in case of fire .
• AT (Anti-Tracking): Applied in high-voltage aerial cables to prevent electrical tracking along the sheath .
• Thermoplastic jackets: Often used in loose tube or ADSS cables for flexibility and water-blocking compatibility .

Sheath Types

• Single Sheath: Provides basic protection; suitable for shorter spans or lower mechanical stress .
• Double Sheath: Offers higher mechanical strength and environmental protection; used for longer spans or high-voltage aerial installations .
• Armored Sheath: Includes metallic or marine-grade bronze braid for enhanced tensile strength and rodent protection .

Typical Dimensions

• Outer Diameter: Varies with fiber count and construction; for example, 2.4 mm for 96-fiber multitube single sheath cables, and 6–12 mm for armored outdoor cables .
• Sheath Thickness: Usually ranges from 0.5 mm to 2 mm depending on material and application; armored cables may have additional layers of metal braid or armor.
• Loose Tube Diameter: Thermoplastic tubes containing fibers typically range from 2 mm to 3 mm .
• Filler Rods and Strength Members: Thermoplastic rods and aramid yarns are used to maintain round shape and provide tensile strength .

Mechanical and Environmental Properties

• Tensile Strength: ADSS cables can be designed for Maximum Allowable Tension (MAT) of 80–400 m spans .
• Crush Resistance: Armored and gel-free cables are tested to IEC 60794 standards for mechanical stress .
• Water Blocking: Water-swellable yarns or tapes prevent moisture ingress .
• Temperature and UV Resistance: PE and AT jackets provide stability in outdoor environments, including high UV exposure .

Summary

Fiber optic cable sheaths are engineered to protect fibers from mechanical, environmental, and electrical hazards. Selection depends on installation type (indoor, outdoor, aerial, buried), fiber count, and environmental conditions. Key considerations include material type, sheath thickness, diameter, tensile strength, and water-blocking features to ensure long-term performance and compliance with standards such as IEC 60794 and Telcordia GR-20 .