How can double FRP self-supporting optical cables ensure long-term tensile strength when installed overhead over short spans?
Publish Time: 2025-10-28
In modern communication network construction, especially in urban areas, rural roads, and industrial parks, self-supporting optical cables have become a mainstream choice for overhead installation due to their advantages, including the elimination of additional messenger wires, ease of installation, and low cost. Double FRP self-supporting optical cables, due to their excellent mechanical properties and environmental adaptability, are widely used in short-span overhead lines. However, despite their short spans, optical cables must withstand multiple stresses, including wind loads, ice, temperature fluctuations, deadweight, and unexpected tension. Ensuring stable and reliable tensile strength over long periods of use is crucial for ensuring the continuity and security of communication networks.1. Double FRP Reinforced Core: The Design Advantages of the Core Tensile StructureThe core of double FRP self-supporting optical cables lies in their "double glass fiber reinforced plastic reinforcement." Unlike traditional single FRP or steel wire reinforcements, this structure utilizes two high-strength, high-modulus FRP rods symmetrically distributed along the center or sides of the cable as the primary load-bearing elements. Made of continuous glass fiber filaments encapsulated in epoxy resin, FRP offers exceptionally high tensile strength while being lightweight, corrosion-resistant, non-conductive, and non-magnetic, thus avoiding the issues of metal rust, lightning induction, and electromagnetic interference. In short-span installations, the dual FRP structure not only provides ample tensile strength but also effectively balances forces through the symmetrical arrangement of the two rods, preventing twisting or deformation of the cable under tension and ensuring that the fiber units remain stress-free.2. Scientific Tension Design and Safety Factor AssuranceIn short-span aerial installations, despite the short span, factors such as construction tension, wind vibration, and thermal expansion and contraction can still exert continuous tension on the cable. Double FRP self-supporting optical cables are typically designed with a rated tensile strength of at least 2-3 times the maximum allowable operating tension to ensure ample safety margins in extreme weather conditions. For example, for a typical 50-meter span application, the static tension the optical cable must withstand is relatively low. However, factors such as transient wind pressure and over-tensioning during construction are still considered during design to ensure that the maximum operating tension does not exceed 60% of the RTS, thereby preventing long-term fatigue damage.3. Protection and Stress Isolation of Fiber Optic UnitsTensile strength is not only reflected in the strength members; more critically, it is to ensure that the optical fiber itself is not affected by tensile stress. Double FRP self-supporting optical cables typically adopt a "center tube" or "layer stranded" structure. The optical fiber is placed in a loose tube filled with water-blocking jelly and located at the geometric center of the cable. The FRP strength members absorb all external tensile forces, while the optical fiber units achieve "stress isolation" through the excess length of the loose tube. Even if the cable elongates slightly under tension, the optical fiber is not strained, thus preventing signal attenuation or even breakage caused by micro- or macro-bending.4. Sheath Materials and Structures Enhance Long-Term DurabilityThe outer sheath of optical cables is typically made of highly weather-resistant polyethylene, featuring UV resistance, high and low temperature resistance, and aging resistance, ensuring resistance to brittleness and cracking under long-term outdoor exposure. The sheath and FRP reinforcements are tightly bonded through extrusion or wrapping, forming a stable integral structure that prevents moisture intrusion and mechanical damage. Some high-end products also incorporate water-blocking tape or yarn within the sheath to further enhance waterproofing and prevent material degradation due to moisture penetration.5. Standardized Installation Procedures Ensure PerformanceEven the most sophisticated design relies on standardized installation procedures. For short-span installations, dedicated tensioners and pulleys should be used to prevent direct pulling on the cable and localized damage. Hook spacing should be uniform to avoid excessive or insufficient sag. When securing the terminals, use specialized pre-twisted wire tension clamps or fastening fixtures to ensure uniform tension transfer to the FRP reinforcements, not the sheath or optical fiber. After installation, the cable sag should be checked to ensure it meets design requirements to avoid fatigue fractures caused by prolonged overtightening.6. Long-term monitoring and maintenance improve reliabilityWith the development of intelligent optical cable technology, some double FRP self-supporting optical cables now feature integrated strain sensors to monitor tension changes in real time and detect anomalies promptly. Regular inspections can also promptly identify problems such as sheath wear and loose hooks, eliminating potential risks before they occur.In summary, double FRP self-supporting optical cables achieve excellent tensile strength and long-term reliability in short-span aerial installations through their high-strength FRP reinforcement, scientific structural design, fiber stress isolation, weather-resistant sheathing, and standardized construction. They not only meet the stringent stability and security requirements of modern communication networks, but also offer advantages such as lightness, corrosion resistance, and maintenance-free operation, making them an ideal choice for aerial optical cable deployment.
