Siemens SIMATIC NET PROFIBUS Owner's Manual page 36

Topologies of SIMATIC NET PROFIBUS Networks
Monitoring FO Links
Using the echo function, the connected OLMs can monitor the fiber-optic sections.
A break on a link is indicated by a display LED and by the signaling contact
responding.
Even if only one transmission direction is lost, the segmentation triggered by the
monitoring function leads to safe disconnection of the OLM from the star coupler.
The remaining network can continue to work without problems.
Mixed Structure
The star coupler can be made up with combinations of OLM/P, OLM/G and
OLM/G-1300 modules and at the RS-485 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
ET 200M À
À
4
À Terminating resistor activated
1 FO cable
2 LAN cable for PROFIBUS
Figure 2-5 Network Structure in a Redundant, Optical, Two-Fiber Ring Topology
2-10
S7-400 S7-400
À
2
1
OP 25
À
4
À
1
Path 1
1
Path 2
3 PROFIBUS 830-1T connecting cable
4 PROFIBUS 830-2 connecting cable
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
PG
À
3
À
1