Network topology
4.2 Integration of long FO cable runs
PROFIBUS Optical Bus Terminal (OBT)
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Operating Instructions, 04/2016, C79000-G8976-C122-07
4.2
Integration of long FO cable runs
The maximum permitted length of PCF FO cable with the OBT is 300 m. If longer FO links or
other FO cable types, for example glass graded index fibers or monomode fibers are
necessary, they can be used by combining OBTs with OLMs (Optical Link Module). In this
situation, the OBT is connected electrically with the OLM (OBT/CH 1 to OLM/CH 1) and the
OLM is connected to the long FO cable link. At the end of the FO cable link, the combination
is reversed with a second OLM/OBT pair.
Image 4-1
Example of covering longer FO links with OBTs and OLMs
The maximum permitted transmission speed and the type and maximum length of the FO
cable link is decided by the OLM type.