Technical data

PROFIBUS networks
1.2 Basics of the PROFIBUS network
PROFIBUS Network Manual
22 System Manual, Edition 04/2009, C79000-G8976-C124-03
Restrictions:
● Frame throughput times are increased compared with an electrical network
● The assembly of glass fiberoptic cables with connectors requires specialist experience
and tools
● 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: Fiberoptic cables with glass, PCF or plastic fibers
Maximum link length:
(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 speed: 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.
1.2.5.4 Transmission techniques for PROFIBUS PA
IEC 611582 standard
The transmission technique corresponds to the MBP transmission technique complying with
the IEC 611582 standard (identical to EN 611582).
The transmission medium is a shielded, twisted pair cable. The signal is transmitted
Manchester-coded at 31.25 kbps. In general, the data line is normally also used to supply
power to the field devices.
Benefits:
● Simple cabling with twisted pair
● Remote power supply via the signal cores