I. Function of Strength Members
Optical fiber is primarily composed of high-purity silica, which has low mechanical strength and limited tensile and compressive resistance. During cable installation and long-term operation, the fiber is continuously subjected to external forces such as self-weight, wind and ice loads, and installation tension. Without an effective load-bearing structure, the fiber is prone to micro-deformation, which can lead to signal attenuation. Therefore, optical cables must be equipped with strength members to serve as the load-bearing framework, absorbing the majority of mechanical stress and controlling fiber micro-strain to ensure long-term stable signal transmission.
Strength members commonly used in engineering fall into two main categories: Phosphatized Steel Wire as the primary metallic option, and FRP (Fiber Reinforced Plastic) as the most widely used non-metallic option. The two types offer different performance characteristics, and material selection should be based on the specific application environment.
II. Phosphatized Steel Wire: The Mainstream Choice for Conventional Outdoor Cables
Phosphatized steel wire is the most widely used metallic strength member in outdoor optical cables. Its core advantages lie in the balance between high strength and good process stability. Under the same cross-sectional area, the tensile load capacity of phosphatized steel wire is typically higher than that of FRP, making it suitable for applications with higher mechanical strength requirements.
In terms of environmental adaptability, the phosphating treatment forms a uniform phosphatized film layer on the wire surface. This helps improve corrosion resistance and reduces the risk of interfacial reactions caused by direct contact with compounds such as filling gels, thereby helping to mitigate hydrogen-related risks during long-term cable operation.
Phosphatized steel wire is suitable for GYTA and GYTS stranded loose tube cables, central tube cables, flame-retardant mining cables, as well as direct-buried cables and various outdoor cable types that utilize gel filling systems.
III. FRP: A Core Material for Special Applications
FRP (Fiber Reinforced Plastic) is formed by a pultrusion process using continuous glass fibers as the reinforcement framework and epoxy or vinyl ester resin as the matrix. It is a widely used structural material among non-metallic strength members. Its core value lies in its electrical insulation, corrosion resistance, and light weight.
Unlike metallic strength members, FRP is a non-conductive material. It avoids current conduction and electromagnetic coupling effects and does not undergo electrochemical reactions with gel filling systems. Therefore, from a structural design perspective, it helps reduce hydrogen generation risks associated with metals. Its density is approximately one-quarter that of steel, significantly reducing the overall weight of the optical cable and facilitating installation and transportation. Additionally, FRP has a low coefficient of thermal expansion, which helps maintain fiber excess length stability under temperature fluctuations and reduces the risk of micro-bending loss.
FRP is mainly used in aerial cables installed in lightning-prone areas and environments with strong electromagnetic interference, all-dielectric FTTH drop cables, cables used in highly corrosive environments such as coastal salt spray and chemical plants, as well as special cable structures including submarine cables.
IV. Selection Principles for the Two Types of Strength Members
Phosphatized steel wire and FRP are not simple substitutes for one another; rather, they are complementary in function. Rational material selection should be based on the actual service conditions of the cable:
Conventional outdoor aerial, direct-buried, mining, and gel-filled cables – Phosphatized steel wire is generally the preferred choice. Its high strength, mature processing technology, and wide applicability make it a mainstream solution validated by long-term engineering practice.
Lightning-prone areas, substations, and other scenarios with strong electromagnetic interference – An all-dielectric FRP structure should be used to reduce conductivity risks and improve system safety.
Highly corrosive environments such as coastal areas and chemical plants – FRP offers more stable long-term performance due to its excellent corrosion resistance.
FTTH drop cables – FRP is often the preferred choice due to its insulating properties. For indoor-outdoor transition scenarios that require higher tensile strength or long-span installation, metallic strength members may be selected based on the cable design.
V. Conclusion
Strength members directly affect the mechanical service life and transmission stability of optical cables. With its high strength, good process compatibility, and proven engineering performance, Phosphatized Steel Wire has become an important metallic strength material for various conventional outdoor cables. FRP, with its advantages in electrical insulation, interference immunity, corrosion resistance, low density, and structural stability, plays a key role in complex and special service conditions.
As a professional supplier of cable materials, ONE WORLD continues to provide phosphatized steel wire, FRP, and other cable strength member materials to our customers. We also offer material selection recommendations and related technical support. For specific project inquiries, please feel free to contact us.
Post time: May-28-2026