Standard value of pull-out strength of optical fiber cable

The standard pull-out (tensile) strength of typical optical fiber cables ranges from 1.8 kN to 4.5 kN for short-term installation, with long-term operating loads significantly lower, often around 600 lbf (≈2.7 kN).

Overview of Tensile Strength

The tensile strength of an optical fiber cable represents the maximum pulling force the cable can withstand without damage to the fibers or degradation of optical performance. It is not the breaking strength of the cable but a safe limit for installation and operation . Tensile strength is categorized into:

• Installation (short-term) tensile strength: Maximum force applied during pulling or installation, typically ranging from 1,800 to 4,500 N (≈400–1,000 lbf) depending on cable type and construction .
• Operating (long-term) tensile strength: Maximum force the cable can sustain over its service life, usually well below the installation limit, often around 2.7 kN (≈600 lbf) for standard outside plant cables .

Factors Affecting Pull-Out Strength

1. Cable Construction: Kevlar-reinforced or armored cables can handle higher tensile loads (up to 3 kN or more), while tight-buffered or dielectric cables have lower limits (≈1.85 kN for 5.6 mm cables), .
2. Fiber Count and Arrangement: Higher fiber counts or ribbon designs may slightly reduce allowable pull tension due to increased stiffness.
3. Installation Conditions: Pulling through conduits, bends, or ducts increases friction, effectively multiplying the applied tension. Careful monitoring is required to avoid exceeding the cable's rated tensile strength .
4. Environmental Factors: Temperature changes can alter mechanical stress due to differing thermal expansion rates of aramid yarns and glass fibers .

Standard Testing Methods

The IEC 60794-1-21 standard defines mechanical tests for optical fiber cables, including tensile testing. Cables are typically tested over lengths of ≥50 m (or 25 m for specialized cables) using clamping and sheave devices to measure elongation and attenuation under load . Proof testing of fibers ensures minimum strength and removes weak points before cable assembly .

Practical Recommendations

• Always adhere to the manufacturer's specified maximum pulling tension.
• Use steady, continuous pulling; avoid jerking or pushing the cable .
• For long-term reliability, maintain tensile loads well below the installation limit.
• Conduct pre-installation testing for conduit pulls, bends, and friction to prevent microfractures and signal loss . In summary, while the exact pull-out strength varies by cable type, a typical standard for commercial optical fiber cables is 1.8–4.5 kN for installation and ≈2.7 kN for long-term operation, with higher values for reinforced or armored designs.