The function of metal wires in outdoor optical cables

Metal wires in outdoor optical cables primarily provide mechanical strength, environmental protection, and support for installation under tension or harsh conditions.

Mechanical Strength and Load Bearing

Metal wires, often made of high-carbon steel or galvanized steel, are incorporated into outdoor optical cables to bear axial tension during installation and operation, preventing the optical fibers from stretching or breaking under their own weight or external forces such as wind and ice loading . These wires are positioned between the inner and outer sheaths or as part of a steel strand to enhance side pressure resistance and impact resistance, ensuring the cable maintains structural integrity over long spans .

Protection Against Environmental Hazards

Outdoor cables are exposed to mechanical damage, rodents, and extreme weather. Metal wires act as armor, shielding the delicate optical fibers from crushing, abrasion, and accidental impacts . In some designs, such as OPGW (Optical Ground Wire) or OPPC (Optical Phase Conductor) cables, metal wires also provide lightning protection and grounding, allowing the cable to safely carry short-circuit currents while simultaneously transmitting data .

Installation and Tension Management

During stringing and installation, outdoor optical cables are subjected to pulling forces and bending. Metal wires ensure that the cable can withstand these forces without exceeding the maximum permissible tension, preventing fiber damage and maintaining signal integrity . The wires also help maintain the cable's shape and stability, especially in aerial installations where sag and wind-induced oscillations are concerns.

Comparison with Non-Metallic Reinforcements

While non-metallic materials like FRP (Fiber Reinforced Plastic) or aramid yarn provide tensile strength without electrical conductivity, metal wires are preferred when armor, grounding, or high mechanical load capacity is required . Non-metallic reinforcements are lighter and immune to corrosion or induction currents, but they cannot replace the protective and conductive functions of metal wires in certain outdoor applications.

Summary

In outdoor optical cables, metal wires serve multiple critical functions:

• Tensile strength to support long spans and installation tension
• Mechanical protection against crushing, impact, and rodents
• Electrical grounding and lightning protection in hybrid cables like OPGW/OPPC
• Structural stability for aerial or harsh-environment deployments These functions ensure that optical fibers remain protected, operational, and reliable in outdoor and high-stress environments .