ABB AC 800M

Fieldbus Topologies with fibre optics Section 3 Fieldbus Topologies
84 3BDS009029R5001 B
Fieldbus Topologies with fibre optics
Bus length and speed
An optical network can be implemented in a bus, star or ring topology using optical
link modules. The maximum distance between two optical link modules can be up
to 15 km with glass fiber-optic cables, 50 m with plastic fiber-optic cables and with
PCF (Polymer Cladded Fiber) up to 300 m.
The transmission rate can be adjusted in steps from 9.6 kbit/s to 12 Mbit/s,
depending on the hardware.
Mixed structures combining electrical and optical networks are possible. The
transition between the two media is provided by the optical link module. In the
communication between the stations on the bus, there is no difference between two-
wire and fiber-optic technology. Up to 126 stations may be connected to a
PROFIBUS network.
The optical transmission method offers the following advantages:
• Plastic, PCF or glass fiber-optic cables are insensitive to electromagnetic
radiation and make the EMC measures necessary in electrical networks
superfluous.
• In outdoor installations, there is no need for lightning protection measures.
• Fiber-optic cables make floating connections between the system components.
This means that there is no need for expensive equipotential bonding measures.
• Fiber-optic cables can cover long distances between stations.
• Galvanic isolation.
• Either plastic, PCF or glass fiber-optic conductors can be implemented
The optical link modules are suitable for connecting glass or plastic fibre optical
cables with BFOC/2.5 connectors. Depending on the topology, the fibre material,
the fibre diameter, the wavelength of the light and the path attenuation, distances of
up to 15 km and more can be bridged. For detailed information on the devices,
please refer to the manufacturer's product descriptions and operating instructions
.