Technical data

Topologies of SIMATIC NET PROFIBUS networks
2.2 Topologies of optical networks
PROFIBUS Network Manual
28 System Manual, Edition 04/2009, C79000-G8976-C124-03
2.2 Topologies of optical networks
2.2.1 Electrical - optical gateway
Electrical/optical conversion
If you want to cover larger distances with the fieldbus regardless of the transmission rate or if
the data traffic on the bus is threatened by extreme levels of external noise, you should use
fiberoptic cables instead of copper cable.
To interface electrical cables with fiberoptic cables, you have the following possibilities:
● PROFIBUS nodes with a PROFIBUS-DP interface (RS-485) are connected to the optical
network via an Optical Bus Terminal (OBT) or via an Optical Link Module (OLM).
● PROFIBUS nodes with an integrated fiber-optic cable interface (for example the ET 200M
(IM 153-2 FO), S7-400 (IM 467 FO)) can be directly integrated in an optical network with
a bus topology.
● Optical networks with a larger network span or structured as redundant rings should be
implemented using OLMs.
The structure of optical networks using optical link modules (OLMs) is described in detail in
later chapters in this manual.
For information about the structure of an optical PROFIBUS network with PROFIBUS nodes
having an integrated FO interface, refer also to the manual Distributed I/O System ET 200"
(
http://support.automation.siemens.com/WW/view/en/114247).
2.2.2 Topology with integrated optical interfaces
Bus topology
The optical PROFIBUS network with nodes that have an integrated fiber-optic cable interface
has a linear (bus) topology. The PROFIBUS nodes are interconnected in pairs over duplex
fiber-optic cables.
Up to 32 PROFIBUS nodes with integrated FO interfaces can be connected in series in an
optical PROFIBUS network. If a PROFIBUS node fails, the linear topology means that none
of the downstream DP slaves can be accessed by the DP master.