Siemens SIMATIC NET PROFIBUS Betriebsanleitung PDF herunterladen (Seite 17)

Network Topologies

3.3 Ring Topology

SIMATIC NET PROFIBUS Optical Link Module OLM V4.0

Operating Instructions, 01/2013, C79000-G8976-C270-03

Note:

Unused optical channels you intend to use later to expand the network cause a broken fiber-

optic cable signal if the monitoring is active. You can avoid this error message by setting

unused channels to the mode “bus without fiber-optic link monitoring”. Remember that the

optical channels that are not connected must be protected against external light and pollution

by protective caps.

3.3 Ring Topology

3.3.1 Redundant Optical Ring

Figure 3-3 Network structure with a redundant optical ring topology

* If OLM / P22 or OLM / G22 are used, an additional DTE or bus segment

can be connected to Ch 0.

This network topology is a special form of the bus topology. “Closing” the optical bus

achieves high operational reliability in the network. A redundant optical ring can only be

implemented using modules with two optical channels.

Monitoring mechanisms:

• Send echo: yes

• Monitor echo: yes

• Suppress echo: yes

• Segmentation: yes

The interruption of one or both fiber-optic cables between the modules is detected by the

OLM and the ring becomes an optical bus.

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Siemens SIMATIC NET PROFIBUS Betriebsanleitung Seite 17