The outer sheath of optical cables is typically made from materials like PVC, PE, LSZH, or specialized compounds, chosen for protection, durability, and environmental resistance.

Purpose of the Outer Sheath

The outer sheath serves as the primary protective layer for optical fibers, shielding them from mechanical damage, moisture, chemical corrosion, UV radiation, and fire hazards. It also contributes to the cable's tensile strength, flexibility, and abrasion resistance during installation and operation .

Common Outer Sheath Materials

• PVC (Polyvinyl Chloride): Widely used due to its low cost, chemical resistance, weathering resistance, and moderate flame retardancy. PVC is suitable for general indoor and outdoor applications but produces dense smoke and toxic gases when burned .
• PE (Polyethylene): Known for excellent low-temperature performance, UV resistance, chemical stability, and electrical insulation. PE is often used in outdoor environments, with variations like MDPE (medium density) and HDPE (high density) for added toughness .
• LSZH (Low Smoke Zero Halogen): Flame-retardant material that produces minimal smoke and no toxic halogen gases during combustion. LSZH is ideal for indoor installations, especially in confined spaces like data centers, where fire safety is critical .
• Other specialized materials:
  • AT (Armored or Rodent-Proof Sheaths) for protection against physical damage or pests.
  • PVDF, Plenum, Riser, and Polyurethane (PU) for specific applications such as high chemical resistance, underwater use, or compliance with building fire codes .

Selection Considerations

Choosing the right sheath material depends on installation environment and safety requirements:

• Outdoor: PE or HDPE for UV, moisture, and temperature resistance.
• Indoor: LSZH for low smoke and non-toxic emissions.
• Industrial: PVC or TPE for chemical and oil resistance.
• Submarine or wet environments: PU for water and abrasion resistance .

Summary

The outer sheath material is a critical factor in cable longevity, safety, and performance. PVC, PE, and LSZH are the most common, each offering distinct advantages depending on environmental exposure, fire safety requirements, and mechanical protection needs .