fibre optic comms


Thread Starter


I am looking for an end-to-end solution for transmitting a single status point (relay contact) between two sites that have a fibre optic cable connection. I need to repeat the contact status remotely as a secure dedicated signal.

Fibre cable is multimode 62.5/125um less than 1km long. There are 2 spare cores.

Can anyone please advise any suitable product that can be used in this application.
I'm not sure formal off-the-shelf products can do this - unless you want to add a full signal MUX.

Any externally powered (by AC power pack or DC) RS-232 to Fiber converter could be used. In the relay "normal" case, have the relay pull (assert) the RS-232 Rxd input to +5 to +12v with reference to the RS-232 signal ground. In the relay "abnormal" case, have the relay pull (deassert) the RS-232 Rxd input to -5 to -12v.

This will cause the fiber to be lit in normal cases (likely drawing 100mA or so of power! make sure this doesn't over-heat the converter as many cheap RS-232/Fiber products assume an async signal which mixes 0's and 1's and thus isn't driving the fiber 100% duty cycle) and dark in abnormal/alarm cases.

At the receiving end, you'll need to find a small solid-state-relay or driver which can use the 3-5mA RS-232 Txd output. When lit (normal), this pin will be about +9 to +12v, but can only drive 3-5mA. When dark (abnormal), this pin will be about -9 to -12v.=20

Best Regards

Lynn August Linse, Senior IA Application Engineer
15353 Barranca Parkway, Lantronix Inc, Irvine CA 92618
[email protected]
Tel: (949)279-3969 Fax: (949)453-7152