The radius below which an optical Fiber or fiber-optic Cable should not be bent.

Note 1: The minimum Bend Radius is of particular importance in the handling of fiber-optic cables. It will vary with different cable designs. The manufacturer should specify the minimum radius to which the cable may safely be bent during installation, and for the long term. The former is somewhat shorter than the latter.

Note 2: The minimum bend radius is in general also a function of tensile stresses, e.g., during installation, while being bent around a sheave while the fiber or cable is under tension.

Note 3: IF no minimum bend radius is specified, one is usually safe in assuming a minimum long-term low-stress radius not less than 15 times the cable diameter.

Besides mechanical destruction, the other reason why one should avoid excessive bending is to minimize Microbending losses. Microbending losses are Light Attenuation that are induced by deformity (clinks) on the fiber while Macrobending are the linkage of light through the fiber cranding. This is more likely to happen when the fiber is excessively bent.

A minimum bend radius is the function of the material and has little or nothing to do with the press brake punch tip. A minimum bend radius for one material thickness is not the SAME for another material thickness.

Fiber Optic Cable has a minimum bending radius, specified by the manufacturer, for loaded conditions, such as during cable pull, and for unloaded conditions, such as the time after the cable has been installed and is in its final resting position.