Technical data

Network configuration
3.2 Configuring optical networks
PROFIBUS Network Manual
48 System Manual, Edition 04/2009, C79000-G8976-C124-03
Configuration
When configuring an electrical network with RS485 repeaters, the following conditions must
be taken into account:
● The maximum segment length for a transmission speed must be adhered to (see section
Segments for transmission speeds up to a maximum of 500 kbps (Page 42),
section
Segments for a transmission speed of 1.5 Mbps (Page 43), section Segments for
transmission speeds up to a maximum of 12 Mbps (Page
46)).
● The maximum number of bus attachments (stations, RS-485 repeaters, OLM) per
segment is limited to 32. There may be further restrictions at transmission speeds of
1.5 Mbps or higher (see section
Segments for a transmission speed of 1.5 Mbps
(Page
43)).
● The maximum number of nodes in a network is limited to 127.
● A maximum of 9 RS485 repeaters can be installed between two nodes.
3.2 Configuring optical networks
3.2.1 Overview
Configuration parameters for optical networks
When configuring optical PROFIBUS networks, the following parameters must be taken into
account:
● Using fiberoptic cables, only pointtopoint links can be established.
● The maximum signal attenuation of the transmission path (the power budget) must be
within the permitted values.
● The minimum or maximum permitted transmission speeds of the components (only one
uniform transmission speed can be used in a network).
● The cascading rules for the components used.
● The maximum permitted number of nodes in a network.
● In largespan networks, the transmission delay time.
3.2.2 How a fiberoptic cable transmission system works
Introduction
This section describes the structure and functions of an optical transmission system. The
information here will help you to understand the rules for calculating the optical power budget
in the next section.