Technical data

Network configuration
3.2 Configuring optical networks
PROFIBUS Network Manual
System Manual, Edition 04/2009, C79000-G8976-C124-03
53
Table 3- 9 Permitted cable lengths in an OLM network
Fiber-optic cables
SIMATIC NET
PROFIBUS
Maximum cable
lengths between two nodes
(in m)
Projected for 1 network
(= 32 nodes) (in m)
Plastic fiberoptic,
duplex cord
50 1550
Plastic fiberoptic,
standard cable
80 2480
PCF fiberoptic,
standard cable
400 12400
Note
An optical bus can contain a maximum of 32 integrated optical interfaces in series.
Several buses of up to 32 integrated optical interfaces can only be linked via OBTs (optical
repeaters).
In optical networks (bus, star, ring) containing only OLMs, the number of OLMs is limited to
122.
The number of all optical components (integrated interfaces, OBTs, OLMs) in the optical
PROFIBUS network must be specified in the configuration tool as the "Number of OLM,
OBT" parameter (see Section
Frame transmission time (Page 58)). This number must not
exceed 122.
Mixing plastic fiberoptic and PCF fiberoptic
To make the best use of the different cable lengths, the plastic fiberoptic cables and PCF
fiberoptic cables can be mixed.
For example, you can use plastic fiber-optic cable for local connections between distributed
DP slaves (distance < 50 m) and PCF fiber-optic cable for the connection between the DP
master and the first DP slave in the bus topology (distance > 50 m).