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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 fiber 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.
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 fiber 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.
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
