Table of Contents
Advertisement
Connecting fibre optic cables
Minimum bend radius
All optical fibres have a minimum bend radius. This represents the smallest
circle that is allowed to be formed from a loop of fibre, that is how tight it can be
coiled, looped or bent.
If fibres are bent tighter than the minimum bend radius then two possible effects
can happen:
S
S
For glass fibres (orange or green outer sheath) the long term minimum bend
radius is approximately 30 mm.
Figure 3-35 illustrates the minimum bend radius for fibre optic cables.
If the fibre is under tension (being stretched), the bend radius should be much
larger, at least doubled. This is because the tension in the fibre can increase
the possibilities of damage.
If in doubt about the radius, the fibre should be allowed to form its natural bend
radius by allowing it to bend under gravity only. This natural bend radius is
normally greater than 30 mm.
Inst. 3–58
CAUTION
Under no circumstances should fibres be bent tighter than
the minimum bend radius.
Excessive light loss can occur from the outside of the bend, resulting in a
loss of performance.
The fibre can fracture due to microscopic imperfections in the surface.
This type of break is invisible externally. If such a break occurs, excessive
light loss would be permanent and light would be scattered and reflected
from the break in the fibre. Returning the fibre to straight will not help and
the whole assembly will require replacement.
30 mm
FIBRE OPTIC CABLE
Figure 3-35 Minimum bend radius of 30 mm
Installation & Configuration: Horizon macro outdoor
68P02902W03-A
CONTROLLED INTRODUCTION
GSM-204-423
31st Oct 01
Advertisement
Table of Contents
