Technical data
PROFIBUS networks
1.2 Basics of the PROFIBUS network
PROFIBUS Network Manual
System Manual, Edition 04/2009, C79000-G8976-C124-03
21
Note
The properties listed in the table above assume a bus cable of type A and a bus terminator
according to the PROFIBUS standard IEC 61158-2 / EN 61158-2. The SIMATIC
NET PROFIBUS cables and bus connectors meet this specification. If reductions in the
segment length are necessary when using special versions of the bus cable with increased
loop resistance, this is pointed out in the sections on "Configuration" and "SIMATIC NET
PROFIBUS cables".
1.2.5.3 Transmission techniques for optical components
The IEC 61158-2 / EN 61158-2 guideline
The optical transmission technique complies with IEC 61158-2 / EN 61158-2.
Integrated optical interfaces, OBT, OLM
The optical version of SIMATIC NET PROFIBUS is implemented with integrated, optical
ports, optical bus terminals (OBT) and optical link modules (OLM).
Duplex fiberoptic cables are used as the medium made of glass, PCF or plastic fibers.
Duplex fiberoptic cables consist of 2 conducting fibers surrounded by a common jacket to
form a cable.
Modules with integrated optical ports and optical bus terminals (OBTs) can be
interconnected to form optical networks only with a bus structure.
Using OLMs, optical networks can be installed using a bus, star and ring structure. The ring
structure provides a redundant signal transmission path and represents the basis for
networks with high availability.
Benefits:
● Regardless of the transmission rate, large distances can be covered between two end
devices (connections between OLM and OLM up to 15,000 m)
● Electrical isolation between nodes and transmission medium
● When plant components at different ground potential are connected, there are no shield
currents
● No electromagnetic interference
● No additional lightning protection elements are required
● Simple laying of fiberoptic cables
● High availability of the LAN due to the use of a ring topology
● Extremely simple attachment technique using plastic fiberoptic cables over shorter
distances