Siemens SIMATIC NET PROFIBUS User Manual
Page 39
Topologies of SIMATIC NET PROFIBUS Networks
2-13
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
2.2.3
Combination of Integrated Optical Interfaces and OLMs
Note
The optical ports of the OLMs are optimized for greater distances. The direct
coupling of the optical ports of an OLM with an OBT or integrated optical ports is
not possible due to differences in the technical specifications.
Attaching Glass FO Cables to Buses Made up of Integrated Optical Interfaces
The operating wavelength of the integrated optical interfaces and the OBT is
optimized for the use of plastic or PCF fibers. The direct attachment of glass FO
cables is not possible.
If a link with glass FO cable is required, for example to span distances of more
than 300 m, this link must be implemented with OLMs. The attachment of glass
links to the optical bus made up of integrated optical interfaces is via the RS-485
interface of an OBT. The following schematic shows an example of an application:
Further
nodes
Field device without
FO interface
А
А
3
PG
À
ET 200M with
IM 153-2 FO
OBT
OBT
OBT
OBT
3
1
1
2
4
1
1
À
1
1 FO cable
2 LAN cable for PROFIBUS
3 PROFIBUS 830-1T connecting cable
4 PROFIBUS 830-2 connecting cable
À
Terminating resistor activated
up to 15 km
А
А
А
А
Figure 2-7
Attachment of an Optical Glass Link to an Optical Bus Made up of Integrated Optical
Interfaces