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1
Establish the stiffness coefficient from the table below: the stiffness coefficient
is a figure used to represent the diameter and the stiffness of a cable. This
figure is only relevant in the context of setting the torque, it has no other
relevance. The higher the U figure the stiffer the cable. There is a degree of
subjectivity about determining the cable stiffness. What is low stiffness? What
is high stiffness? Determining this (the stiffness) relies upon the user having
some familiarity with bundled optical fibre cables, this will give the experience to
assess whether the cable has low, medium or high stiffness. For instance a
small diameter cable with high stiffness may be less stiff than a large cable with
medium stiffness. The table reflects this. If there is any doubt, in the first
instance err on the low side, i.e. select a lower U figure.
Cable dia (mm)
Cable stiffness
Stiffness coefficient (U)
2.0 - 3.5
Low
U1
Medium
U1
High
U2
3.5 - 5.0
Low
U1
Medium
U2
High
U3
5.0 - 6.5
Low
U2
Medium
U3
High
U5
6.5 - 8.0
Low
U2
Medium
U4
High
U6
2
Assess the coefficient of friction of the cable insulation (the outer coating). Is it
low or high. Once again this relies on the user having some experience with
bundled optical fibre cables. As a guide, if the surface feels smooth and dry the
coefficient of friction will be low, if you slide your hand over the surface does it
snatch your flesh? If it does the coefficient of friction will be high. As above, if
there is any doubt, err on the low side i.e. select a lower coefficient of friction.
