Minimum Bending Radii
According to a draft version of EIA-568, the minimum bend radius for UTP is 4 times
outside the cable diameter, or about one inch. For multi-pair cables
the minimum bending radius is 10 times outside diameter. The minimum
bend radii for Type 1A Shielded Twisted Pair (100 Mb/s SRP) is 7.5
cm (3-in.) for non-plenum cable, 15 cm (6-in.) for the stiffer
For optical cables not under tension, the minimum bend radius is 10 times the cable diameter; for cables under tension, it is no less than 20
times the cable diameter. The standard goes on to state that no optical cable will be bent on a radius less than 3.0 cm. (1.18 in.).
A different standard, ISO DIS 11801 (essentially a parallel standard to the one mentioned above), for 100 ohm and 120 ohm balanced cable
lists three different minimum bend radii. Minimum for pulling during installation is 8 time cable diameter, minimum installed radius is 6
times for riser cable, and 4 times cable diameter for horizontal runs. For fiber optic cables, the requirements are the same as those stated
Some manufacturers recommendations differ from the above, so it is worth checking
the spec sheet for the cable you plan to use.