The PE outer sheath serves as the primary protective layer for optical cables, providing mechanical strength, environmental resistance, and long-term durability.

Mechanical Protection

The PE (polyethylene) outer sheath acts as the first line of defense for optical fibers, shielding the delicate internal fibers from physical damage such as crushing, impact, and abrasion during installation or handling. High-density polyethylene (HDPE) sheaths offer compressive strength above 25 MPa, making them suitable for direct burial, overhead, and other demanding laying environments. The smooth surface of PE (friction coefficient ≤ 0.15) also facilitates easier installation in conduits and reduces wear on the cable during movement or pulling .

Environmental Resistance

PE sheaths provide excellent resistance to environmental factors. They prevent moisture ingress, which could degrade the internal insulation and compromise signal transmission. Additionally, PE is resistant to ultraviolet (UV) radiation, chemical corrosion, and temperature extremes, maintaining flexibility in environments ranging from -60℃ to 80℃. This ensures that the optical cable can operate reliably in outdoor and harsh conditions for extended periods .

Longevity and Safety

The PE outer sheath contributes to the long-term stability of optical cables, with outdoor service life exceeding 20 years when properly formulated. PE can be combined with additives such as anti-UV agents or flame-retardant compounds (e.g., LSZH formulations) to enhance performance in specific applications. These formulations reduce smoke and toxic gas emissions in case of fire, making PE sheaths suitable for both outdoor and indoor installations .

Structural Role

Beyond protection, the PE sheath helps maintain the cable's structural integrity by bundling the internal fibers, fillers, and protective layers into a cohesive unit. This containment preserves the cable's geometry, ensuring consistent optical performance and ease of handling during installation .

Summary

In summary, the PE outer sheath in optical cables is essential for mechanical protection, environmental resistance, structural integrity, and long-term reliability. Its selection is critical for ensuring that optical fibers maintain signal quality and durability across various deployment scenarios, including underground, aerial, and outdoor installations .