Siemens SIMATIC NET PROFIBUS, Owner'S Manual, Page: 83 / 490

Configuring Networks
3-17
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
3.2.3 Cable Lengths for Plastic and PCF FO Paths
The length of the transmission path on fiber-optic cables is not dependent on the
transmission rate.
Each node on the optical PROFIBUS network has repeater functionality so that the
following distance information relates to the distance between two adjacent,
interconnected PROFIBUS nodes.
The maximum cable length between two PROFIBUS nodes depends on the type
of fiber-optic cable used and the optical network components.
Table 3-7 Permitted Cable Lengths with Integrated Optical Interfaces or OBT
Fiber-optic cable
SIMATIC NET
PROFIBUS
Maximum cable
lengths between two
nodes (in m)
For 1 Network (= 32
nodes) (in m)
Plastic fiber-optic,
duplex cord 50 1550
Plastic fiber-optic,
standard cable 50 1550
PCF fiber-optic,
standard cable 300 9300
Table 3-8 Permitted Cable Lengths in an OLM Network
Fiber-optic cable
SIMATIC NET
PROFIBUS
Maximum cable
lengths between two
nodes (in m)
For 1 Network (= 32
nodes) (in m)
Plastic fiber-optic,
duplex cord 50 1550
Plastic fiber-optic,
standard cable 80 2480
PCF fiber-optic,
standard cable 400 12400
Note
S
Optical buses can contain max. 32 integrated optical interfaces in series.
S
Several buses of up to 32 integrated optical interfaces can only be linked
via OBTs (optical repeaters).
S
In optical networks (bus, star, ring) containing only OLMs, the number of
OLMs is limited to 122.
S
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
3.3). This number must not exceed 122.