Siemens SIMATIC NET PROFIBUS, Owner'S Manual, Page: 23 / 490

PROFIBUS NETWORKS
1-13
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
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: Bus structure with integrated optical ports and OBT;
bus, star or ring structure with OLMs
Medium: Fiber-optic cables with glass, PCF or plastic fibers
Link lengths
(point-to-point) 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
Transmission rate: 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
Number of nodes: Maximum of 127 per network (126 with ring structure with OLMs)
* 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.