Why are there two bend radius values for each fiber optic cable?

The bend radii for each fiber optic cable define the minimum radius amount of bending each cable should be bent during installation and after installation. This is information is provided to ensure the fiber optic cable is not damaged during installation. Due to the stresses applied to the cables during installation, a larger bend radius is used. After a cable is pulled in, it can be positioned with a smaller bend radius to accommodate pathways, enclosures or work boxes. 

To better clarify what a bend radius is, picture a circle with a point in its center. The radius is the distance from the center to the edge of the circle. Now envision the circle as a pipe. When you know the radius of a circle, you can double it to get the diameter of a pipe. This size pipe would be the smallest size pipe you would want to bend the cable around. For example, if the bend radius for a .47 inch cable is 15X when under load (being installed) and 10x with no load (static, not being pulled), it means that when being pulled in, the cable should not be pulled around a pipe any smaller than 7.05 inches. When the cable is not under load, it can be laid around a pipe that is 4.7 inches in diameter. However, it is not recommended that a cable be pulled around a pipe. 

The information is intended to identify just how small of an angle a cable should subject to when installed and static. Logically, larger cables require larger bend radii. It should be noted that fiber optic cables with bend-insensitive glass are less susceptible to performance loss due to bending. However, the jacket construction could be damaged if the proper bend radii are not adhered to.

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