Siemens SIMATIC S7-400H System Manual page 348

Synchronization modules
18.2 Installation of fiber-optic cables
Pressure
Do not exert any pressure on the cable, for example, by the inappropriate use of clamps
(cable quick-mount) or cable ties. Your installation should also prevent anyone from stepping
onto the cable.
Influence of heat
Fiber-optic cables are highly sensitive to direct heat, which means the cables must not be
worked on using hot-air guns or gas burners as used in heat-shrink tubing technology.
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System Manual, 03/2012, A5E00267695-11
S7-400H