Thickness of Auxiliary Materials for Overhead Line Optical Cables

Auxiliary materials in overhead optical cables, such as OPGW and ADSS, include stainless steel, aluminum, buffer tubes, and protective jackets, with thicknesses designed to balance mechanical strength, corrosion resistance, and fibre protection.OPGW Cable ConstructionOPGW (Optical Ground Wire) cables integrate optical fibres within a protective metallic structure. The auxiliary materials include:Stainless steel and aluminum strands: These form the outer layers of the cable, providing mechanical strength and corrosion resistance. Stainless steel strands are typically used in the core or lateral positions to allow elongation and sag without stressing the fibres, while aluminum provides lightweight corrosion protection . The thickness of these metallic layers is optimized to maintain electrical and mechanical properties while minimizing weight.Loose buffer tubes: Optical fibres are housed in helically stranded tubes filled with jelly to prevent strain. The tube walls are generally thin (fractions of a millimeter) but sufficient to protect fibres from mechanical stress and environmental factors .Jelly filling: Provides cushioning and moisture protection for fibres inside the tubes.Spiral Space® units: Some designs use a hollow, spiraling channel to allow high fibre counts in a compact tube, reducing fibre strain during installation and operation .ADSS Cable ConstructionADSS (All-Dielectric Self-Supporting) cables use auxiliary materials differently:Dielectric strength members: Fibreglass or aramid yarns provide tensile strength without metallic components, with thicknesses sufficient to support spans up to 67 meters in extreme environments .Cable jacket: The outer polymer layer protects against UV, temperature extremes, and mechanical abrasion. Typical jacket thickness ranges from 2–5 mm depending on voltage exposure and environmental conditions .Messenger wire (if used): In messenger-supported designs, a steel wire embedded within the jacket supports the cable weight. The wire diameter is usually 1.8–2.2 mm, with spacing and lashing designed to maintain mechanical stability .Design ConsiderationsThe thickness of auxiliary materials is determined by:Mechanical load: Wind, ice, and sag requirements dictate the strength and thickness of metallic or dielectric layers.Environmental protection: Corrosion resistance, UV stability, and moisture protection influence jacket and tube thickness.Fibre strain minimization: Loose tube and Spiral Space® designs allow fibres to remain stress-free even under elongation or sag .Electrical requirements: For OPGW, metallic layers must maintain grounding and lightning protection capabilities. In summary, auxiliary materials in overhead optical cables are carefully engineered with metallic strands, buffer tubes, and protective jackets whose thicknesses are optimized for mechanical strength, environmental protection, and fibre integrity, typically ranging from fractions of a millimeter for buffer tubes to several millimeters for jackets and metallic layers .