Introduction - Siemens SIMATIC NET OBT Operating Instructions Manual

Introduction

The PROFIBUS OBT (Optical Bus Terminal) it is a network component used in optical PROFIBUS DP
fieldbus networks. It allows the connection of either a single device without an integrated optical
interface or an RS-485 segment to the optical PROFIBUS DP. The following figure shows an
example of a configuration.
Figure 1-1 Example of an optical PROFIBUS DP configuration
Connections
The connection between the individual bus nodes takes the form of an optical bus with two-
fiber plastic fiber-optic cables (plastic fiber-optic cables are also known as POF, Polymer Optical
Fiber) or PCF fiber-optic cables (PCF = Polymer Cladded Fiber, synonymous with HCS1 fiber-optic
cable). Since fiber-optic cables (FO cable) are completely insensitive to EMC interference,
complex grounding concepts and protection measures are unnecessary. This also applies to the
laying of a equipotential bonding cables. Due to be opto-electronic conversion, there is
automatically electrical isolation so that potential differences as can occur in extensive plants are
no longer noticed.
PROFIBUS Optical Bus Terminal (OBT)
Operating Instructions, 06/2022, C79000-G8976-C122-08
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