Universal serial RS232/RS422/RS485 to multimode optic fiber media converter (2 ST type connectors )

NOTE : RD300-OF has reached the end of its life cycle (to know more about its different deadlines click here).


  • 3 in 1 built-in serial interface : RS232/RS422/RS485
  • Serial link up to 2 Mbps for RS422 & RS485 mode, 1 Mbps for RS232 mode
  • Reliable error free communication even in case of EMI/RFI pertubations
  • Fiber length up to 5000 m (100/140 µm fiber type), ST type connectors
  • Automatic RS485 line turn-around, software independent
  • Half-duplex & Full-duplex bidirectionnal data transmission
  • Activity LED for fiber and copper TxD & RxD signals, error LED in case of fiber breakdown
  • Wide DC power range, from +9VDC to +36VDC
  • Point to point mode
  • 15 KV ESD protection and HF filtering on the copper side
  • Robust & compact metal case, CE standards, 35 mm Din Rail mounting


Using fiber optic enables to use a higher communication bandwidth while offering a total immunity against EMI/RFI interferences and an increased security as well.

The optical fibre still offers other advantages : use without risk in an explosive environment, no EMC emission, no ground loops, immunity against lightning and high voltage environments, they are finally lighter, less cumbersome, inert and corrosion resistant ...

Plug & Play: RD300 features a self configuration mechanism based on a CPLD component that frees you from the tiresome operation which consists in the serial parameters setup, product is "Plug & Play".

RD300 features in standard a built-in system to control the fiber integrity, it reports automatically any failure with an error LED and also setups a relay contact (MOSFET) to activate any external safety device.

Its small size, design features and its great adaptability make the RD300 a really universal product capable to satisfy to major needs of the industry.


Technical characteristics





Serial RS232/RS422/RS485 to multimode fiber optic, RS485 mode self line turnaround




Serial speed


2Mbps for RS422/RS485 mode, 1Mbps for RS232 mode






5000m with a 100/140 µm fiber type at 25°C




Serial protocols


The device supports any kind of communication protocols (Modbus, Unitelway, Profibus, DH+ and any ASCII or binary serial protocols ...)






Serial link parameters auto configuration, no switches. Line polarization, termination and selection between RS232/RS422/RS485 modes are configurable by mini-switches.




Serial connectors


Pluggable screw-in terminal, TxD & RxD signal for RS232 mode, TxA, RxA, TxB, RxB for RS422 mode, TRxA & TRxB for RS485 mode




Optic fiber


50/125 µm, 62.5/125 µm, 100/140 µm, 820 nm wave length, selectable ON/OFF state of the fiber light at the idle state.




Power budget


22.4 dB, 5 dB & 11 dB attenuator for short distance communication




Fiber connectors


2 ST connectors




Network topologies


Point to point, ring






2 LEDs Tx/Rx for copper

2 LEDs Tx/Rx for fiber optic n°1

1 LED for fiber n°1 breakdown

1 LED for power






31 RS485 interfaces, 10 RS422 interfaces 




Input load


Input load 1/8 UL in RS485 mode 




EMI/RFI protection


Built-in continuous line surge protection, ESD protection (15 KVeff), HF filtering






Infinite galvanic isolation through the optic fiber






NF EN 55022 emission, NF EN 61000-6-2 immunity






Fiber breakdown self diagnostic, failure is reported on a LED and a relay contact (MOSFET) is activated.




Power supply


+9VDC to +36VDC (pluggable screw-in terminal), 2.1W






Temperature from -5°C to +65°C, storage -40°C to +80°C, relative humidity from 0 to 95% RH without condensation




Dimensions, weight


107 mm (L) x 88 mm (l) x 25 mm (H), 260 g



Point to point topology

This configuration enables to control a single equipment installed in a very polluted or distant area. The optical line is totally insensitive to EMI/RFI perturbations.

Application RD300-OF_1

Simple ring topology

This topology enables to build a simple ring whereas the master equipment is installed in the middle.

Application RD300-OF_2

Technical documentation

NOTE : RD300-OF has reached the end of its life cycle (to know more about its different deadlines click here).

Reference to order





Serial RS232/RS422/RS485 to multimode fiber optic media converter, +9VDC to +36VDC power supply, din rail mounting