Hi everyone, i currently have an old multiplexer which uses a 2 wire long line FM TRX system. I am investigating the possibility of converting this to fibre for increased separation. I have looked into serial to fibre conversion, and am unsure how best to proceed. The specifications of the TRX are as follows :

Mode: Frequency shift key

Logic 'O': 200 KHz
Logic '1': 250 KHz
Baud rate: 50 KHz
Voltage : 20V r.m.s
Transmitter : Push/pull -switching power F.E.T.'s
Receiver :Hard Limiter (better then 7 m.v. sensitivity) Digital correlator (2 MHz sampling, 30 taps) + 5volts 30m.A +/-5%
Filter : Digital correlator (2 MHz sampling, 30 taps)

Medium : RG 108 screen twisted pair to equivalent

I am not sure how to proceed, as i fear that RS to fibre converters will not be able to repeat this type of signal.
Any ideas ?

 

Got got got to ask what this is for. I don't recognize the physical format or frequencies.

But to answer your question, do you want to demodulate the FSK to baseband data and send that over the fiber, or send the FSK directly and demodulate it at the far end of the fiber?

ak

 

Got got got to ask what this is for. I don't recognize the physical format or frequencies.

But to answer your question, do you want to demodulate the FSK to baseband data and send that over the fiber, or send the FSK directly and demodulate it at the far end of the fiber?

ak

Thanks for your reply, This is an old mux system utilised in subsea electronics pods. Its job is to provide a stable 1.5km control system link to subsea equipment. It is actually redundant, but this particular unit has found itself back in service.

To answer your query, the baseband data can be demodulated by the existing TRX. I wasn't clear earlier, this is a 2-way half duplex system, so the solution will also need to be 2-way.

 

So, continuing our game of twenty questions, what you are asking about is a copper FSK to fiber converter on one end, and a fiber FSK to copper on the other end? Can you run duplex fiber, of does it have to be half-duplex also?

Block diagram of current system, schematic, anything?

ak