Siemens SIMATIC NET PROFIBUS Owner's Manual page 23

Restrictions:
S Frame throughput times are increased compared with an electrical network
S The assembly of glass fiber-optic cables with connectors requires specialist
experience and tools
S The absence of a power supply at the signal coupling points (node attachments,
OLMs, OBTs) stops the signal flow
Characteristics of the Optical Transmission Technique
The optical transmission technique has the following characteristics:
Network topology:
Medium:
Link lengths
(point-to-point)
Transmission rate:
Number of nodes:
* not with integrated optical ports and OBT
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.
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
Bus structure with integrated optical ports and OBT;
bus, star or ring structure with OLMs
Fiber-optic cables with glass, PCF or plastic fibers
With glass fibers up to 15,000 m dependent on the fiber and OLM
type
with plastic fibers:
OLM: 0 m to 80 m
OBT: 1 m to 50 m
9.6 Kbps, 19.2 Kbps, 45.45 Kbps, 93.75 Kbps, 187.5 Kbps, 500
Kbps, 1.5 Mbps, 3 Mbps*, 6 Mbps*, 12 Mbps
Maximum of 127 per network (126 with ring structure with OLMs)
PROFIBUS NETWORKS
1-13