Short-term allowable tensile force of optical cable

The short-term tensile strength of fiber optic cables typically ranges from 600 to 4,500 Newtons (approximately 135 to 1,000 pounds), depending on cable design and construction, and represents the maximum pulling force allowed during installation.

Definition and Purpose

Short-term tensile strength, also called installation tensile strength, is the maximum load a fiber optic cable can safely withstand during installation without causing damage to the fibers or degrading optical performance . This is distinct from long-term tensile strength, which applies to the cable after installation under normal operating conditions . Short-term stresses occur during activities such as pulling the cable through ducts, around bends, or from back tension on reels .

Typical Values

• Standard outside plant (OSP) cables: 1,800 to 4,500 N (400 to 1,000 lbf) .
• Tight-buffered cables with dielectric strength elements: 1,850 N for 5.6 mm diameter .
• Kevlar-reinforced cables (6.5 mm diameter): up to 3,000 N with 2% maximum strain .
• Installation limits recommended by manufacturers generally do not exceed 2,700 N (600 lbf) for most commercial cables . These values vary depending on cable construction, fiber count, and reinforcement materials such as aramid yarns or central strength members .

Factors Affecting Short-Term Tensile Strength

1. Cable Design: Core size, cladding thickness, and buffer type influence mechanical strength .
2. Materials: Coatings, sheaths, and strength members (e.g., Kevlar) protect fibers from stress .
3. Environmental Conditions: Temperature, moisture, and UV exposure can reduce tensile performance .
4. Installation Practices: Pulling speed, bend radius, and use of mechanical winches affect the actual stress on the cable .

Installation Guidelines

• Pull cables steadily and continuously, avoiding jerks or pushing .
• Use minimum possible tension and monitor mechanical pulling devices .
• Respect minimum bend radius, typically 20 times the cable diameter under tension .
• Conduct pre-installation testing using tensile and bending testers to prevent microfractures and signal loss .

Standards and Compliance

Short-term tensile strength is defined and tested according to standards such as DIN VDE V 0800-740, DIN EN 50173, and other VDE guidelines, which specify maximum installation forces and testing procedures . Compliance ensures safe installation and long-term reliability of fiber optic networks. In summary, understanding and respecting the short-term tensile strength of optical cables is critical for safe installation, preventing fiber damage, and maintaining network performance. Proper cable selection, handling, and adherence to manufacturer specifications are essential to avoid exceeding these limits.