Siemens SIMATIC NET PROFIBUS manual Star Topologies with OLMs, Optical Channels

Topologies of SIMATIC NET PROFIBUS Networks

Star Topologies with OLMs

Several optical link modules are grouped together to form a star coupler via a bus connection of the RS-485 interfaces. This RS-485 connection allows the attachment of further DTEs until the maximum permitted number of 32 bus attachments per segment is reached.

		S7-400
				Star hub
		À	À
	OP 25
		4
		À	2
	À
	2			2
		1
	À	2		À
		PG
			S7-400
				1
À	Terminating resistor activated		À
			4
	1 FO cable			À
	2 LAN cable for PROFIBUS
	4 PROFIBUS 830-2 connecting cable
Figure 2-4 Example of a Star Topology with OLMs

Optical Channels

The OLMs are connected to the star coupler by duplex fiber-optic cables.

Both DTEs and electrical bus segments can be connected to the OLMs attached by the duplex fiber-optic cables. Depending on the requirements and the distance, the duplex cables can be implemented with plastic, PCF or glass (OLM only) fibers.

PROFIBUS Networks SIMATIC NET	2-9
6GK1970-5CA20-0AA1 Release 2 05/2000