Today is...
Friday, September 22, 2017
Welcome to the Modbus Community, about
the world's leading automation protocol.
Modbus Net Topology Configuration
Is possible having more than one Modbus node after a serial media converter or Is it necessary one for each node (slave)?

We need to separate groups of Modbus devices for electrical safety and I'm thinking use fiber optic. For this aim I'd like to use serial media converter (Fiber optic/Modbus) and create a fiber optic ring. At the beginning of each group of Modbus Devices I'd put a Converter. I'd like to know if Is possible having more than one Modbus node after a serial media converter or Is it necessary one for each node (slave)?
And If ring breaks itself in a point, the communication pass through by the other side or It's broken his too?

thanks in advance

A converter with RS485 output can have more than one device connected (multi-drop).

A device that you could use:
http://www.icpdas-usa.com/i_2541.html

From it's description:
The I-2541 is an RS-232/422/485 to fiber optic converter that ensures data transmission security by using fiber optic transmission technology to provide immunity from EMI/RFI interference.

The I-2541 is designed for RS-232/422 point-to-point connections and RS-485 multi-drop applications which require a signal to be transmitted for distances of up to 2Km (6,600 ft), and is a perfect solution in applications where transmission must be protected from electrical exposure, power surges, lightning strikes or chemical corrosion.

Thanks a lot for reply. It's very useful.

Regards.
Massimo