There are several common materials for optical fiber sheaths

Common optical fiber sheath materials (also referred to as the outer jacket or secondary coating) mainly include the following types, each with distinct characteristics and application scenarios. The primary function of the sheath is to protect the internal fiber core and primary coating, providing mechanical strength, environmental resistance, and ease of installation.

 Primary Materials and Their Differences

 1. PVC (Polyvinyl Chloride)

    Characteristics:

      Wide Application: The most common jacket material for indoor cables. Low cost, good flexibility, and easy to process.

      Flame Retardancy: Self-extinguishing, but produces thick black smoke and releases toxic, corrosive halogenated gases (e.g., hydrogen chloride) when burned.

      Environmental Resistance: Resistant to oils and chemicals, but has moderate tolerance to high and low temperatures (typical operating range: -20°C to +70°C).

    Primary Applications: Indoor cabling, inside buildings, equipment rooms—areas with good ventilation and low occupant density. Not suitable for enclosed spaces or densely populated areas.

 2. LSZH (Low Smoke Zero Halogen)

    Characteristics:

      Safety & Environmental Friendliness: Very low smoke emission and halogen-free when burned, preventing the release of toxic, corrosive gases. This is its core advantage.

      Flame Retardancy: Good flame-retardant properties.

      Mechanical Properties: Slightly harder and less flexible than PVC. Offers good tensile strength.

    Primary Applications: Locations with stringent fire safety requirements, such as data centers, subways, tunnels, high-rise buildings, hospitals, schools, airports, and other crowded or confined spaces. The preferred choice for modern, high-standard cabling.

 3. PE (Polyethylene)

    Characteristics:

      Excellent Outdoor Performance: Superior moisture and water resistance, making it the standard jacket material for outdoor cables.

      Environmental Resistance: Highly resistant to UV (with carbon black additive), chemicals, and extreme temperatures (operating range: -60°C to +80°C).

      Disadvantage: Highly flammable; burns and drips like a candle, facilitating rapid flame spread.

    Primary Applications: All types of outdoor cables, e.g., for direct burial, duct, and aerial installations. Never used indoors.

 4. Polyurethane

    Characteristics:

      Outstanding Mechanical Properties: Exceptional abrasion, flexing, tear, and oil resistance.

      Flexibility: Remains flexible even at low temperatures.

      Cost: Relatively high.

    Primary Applications: Cables for harsh industrial environments, such as robotic cables, cable carrier applications, mining, oil fields, and military field use—where frequent movement and high mechanical stress are expected.

 5. Flame-Retardant PE (FR-PE) or Flame-Retardant Polyolefin

    Characteristics:

      PE or polyolefin material treated with flame retardants, offering decent outdoor performance along with some flame retardancy. However, it does not achieve the low-smoke, zero-halogen level of LSZH.

    Primary Applications: Outdoor or duct installations with specific flame-retardancy requirements, serving as a compromise between PE and LSZH.

 6. Nylon (PA)

    Characteristics:

      Highly abrasion-resistant, smooth surface, chemically resistant. Often used as a thin outer jacket over a PVC or LSZH sheath, forming a composite jacket structure.

    Primary Applications: Enhances cable tensile strength and abrasion resistance. Commonly used in indoor/outdoor cables or installations requiring high reliability.

  Summary Comparison Table

 Selection Guidelines

1.  Indoor vs. Outdoor:

     Indoor Priority: LSZH (safety first), followed by PVC.

     Outdoor Priority: PE (moisture and weather resistance), with FR-PE for special requirements.

2.  Safety Requirements: LSZH is mandatory for crowded or enclosed spaces.

3.  Mechanical Demands: For frequent movement and high-friction environments, consider Polyurethane or Nylon overjackets.

4.  Cost Considerations: PVC is the most economical, provided safety and performance requirements are met.

In summary, choosing an optical fiber sheath material involves balancing mechanical protection, environmental resistance, flame retardancy/safety, and cost based on the specific application. In modern structured cabling, LSZH has become the dominant trend for indoor applications, while PE remains the absolute standard for outdoor use.