Bend Radius and Tensile Loading

An important consideration in fiber-optic cable installation is the cable's minimum bend radius. Bending the cable farther than its minimum bend radius might result in increased attenuation or even broken fibers. Cable manufacturers specify the minimum bend radius for cables under tension and long-term installation. The ANSI TIA/EIA-568B.3 standard specifies a bend radius of 1.0 inch under no pull load and 2.0 inches when subject to tensile loading up to the rated limit.

For ISP cable other than two-fiber and four-fiber, the standard specifies 10 ∴ the cable's outside diameter under no pull load and 15∴ the cable's outside diameter when subject to tensile load. Cable tensile load ratings, also called cable pulling tensions or pulling forces, are specified under short-term and long-term conditions. The short-term condition represents a cable during installation and it is not recommended that this tension be exceeded. The long-term condition represents an installed cable subjected to a permanent load for the life of the cable. Typical loose-tube cable designs have a short-term (during installation) tensile rating of 600 pounds (2700 N) and a long-term (post installation) tensile rating of 200 pounds (890 N).

August 29, 2011

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