Siemens SIMATIC NET PROFIBUS manual Using Long Fiber Optic Sections, OLM/G11 OBT

Network Topology

4.2Using Long Fiber Optic Sections

The maximum permitted length of PCF FO cables with the OBT is 300 m. If longer distances are required with fiber-optic cables, then other fiber-optic types such as graded glass fibers or monomode fibers are necessary and these can be used in a combination of OBT with OLM (Optical Link Module). The OBT is then connected electrically to the OLM (for example OBT/CH 1 to OLM/CH 1) and the OLM is attached to the long fiber-optic section. At the other end of the fiber-optic section, the arrangement is reversed by another OLM/OBT pair.

PC	SIMATIC S7-400	ET 200M with
	with IM 467 FO	FO interface
PG
OP

OBT

À

À

1)

2)

OBT OLM/G11 1)

À

2)

À

OLM/G11

OBT

À

À1)

2)

À Terminating resistor activted

3)

1) PROFIBUS cable (terminated at both ends)

2) Plastic FO cable or PCF FO cable with two fibers

3) FO cable for long distances

Figure 4-1 Example of Including Long Fiber-optic Segments with OBT and OLM

The maximum permitted transmission rate and the type and maximum length of the fiber-optic segment are determined by the OLM type.

4-2	PROFIBUS Optical Bus Terminal (OBT)
	C79000-G8976-C122-02