Tensile load on plastic optical cable

The tensile load on plastic optical cables is the maximum pulling force the cable can withstand without damaging the fibers, defined separately for installation (short-term) and operational (long-term) conditions.

Definition and Importance

Tensile load refers to the maximum force applied along the cable's length that the optical fibers can endure without degradation of optical performance or structural damage. It is not the breaking strength of the cable but a safe limit for installation and operation . Proper adherence to tensile limits ensures signal integrity and prevents fiber breakage or increased attenuation.

Types of Tensile Load

1. Installation (Short-Term) Tensile Load: This is the maximum force the cable can withstand during installation, such as pulling through ducts, around bends, or from reels. Exceeding this limit can damage fibers or the cable jacket. For most fiber optic cables, installation tensile loads should not exceed 2,700 Newtons (≈600 pounds) .
2. Operational (Long-Term) Tensile Load: After installation, the cable experiences lower, sustained forces. The long-term tensile rating ensures the cable maintains performance over its service life under environmental stresses like wind, temperature changes, or building movement .

Factors Affecting Tensile Performance

• Cable Construction: The number of fibers, presence of strength members, and type of jacket material influence tensile strength .
• Protective Layers: Armoring, braid layers, or polymer coatings help distribute stress and prevent fiber elongation .
• Fiber Type: Plastic optical fibers are more flexible but generally have lower tensile strength than glass fibers, requiring careful handling during installation .
• Environmental Conditions: Temperature, humidity, and mechanical vibrations can affect long-term tensile performance .

Testing Standards

• IEC 60794-1-21 specifies non-destructive tensile testing methods, including sample lengths (≥50 m) and clamping techniques to measure elongation and attenuation under load .
• TIA-455-33C provides detailed procedures for tensile and bending tests, ensuring optical performance is maintained under specified loads .
• Tests simulate real-world conditions, including dynamic and cyclic stresses, to predict long-term reliability .

Practical Guidelines

• Pull cables steadily and continuously, avoiding jerks or sudden tension spikes .
• Use mechanical pulling devices cautiously, monitoring tension to stay within manufacturer-specified limits .
• Ensure minimum bending diameters are respected during installation to prevent localized stress on fibers .
• For dynamic applications (e.g., cranes or moving machinery), select cables with reinforced jackets and strength members to withstand repeated tensile and bending loads . By understanding and adhering to these tensile load limits and testing standards, plastic optical cables can maintain mechanical integrity and optical performance throughout their service life.