Technical data

Topologies of SIMATIC NET PROFIBUS networks
2.2 Topologies of optical networks
PROFIBUS Network Manual
32 System Manual, Edition 04/2009, C79000-G8976-C124-03
Mixed structure
The star coupler can be made up with combinations of OLM/P, OLM/G and OLM/G1300
modules and at the RS485 end with all types.
Redundant Optical Rings using OLMs
Redundant optical rings are a special form of bus topology. By closing the optical bus to form
a ring, a high degree of operational reliability is achieved.
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Path 1
Path 2
2 3
1
4
1
OP 25
PG
S7-400S7-400
ET 200M
1
1
① Terminating resistor activated
1 Fiber-optic cables
2 PROFIBUS bus cable
3 PROFIBUS connecting cable 830-1T
4 PROFIBUS connecting cable 830-2
Figure 2-5 Network structure in a redundant, optical, twofiber ring topology
A break on a fiberoptic cable between two modules is detected by the modules and the
network is reconfigured to form an optical bus. The entire network remains operational.
If a module fails, only the end devices or electrical segments attached to the module are
separated from the ring; the remaining network remains operational as a bus.
The problem is indicated by LEDs on the modules involved and by their signaling contacts.
After the problem is eliminated, the modules involved cancel the segmentation automatically.
and the bus is once again closed to form a ring.
Note
To increase the availability, the duplex cables for the outgoing and incoming paths in the ring
should be laid separately.