Strange PLC dialing out to fiber optic...Huh?

I have an older PLC working as a Data acquisition and remote monitoring system on a piece of equipment. The PLC is approximately 1/4mile from an analog phone line connection with a USR V34 RS-232 Courier modem. Fiber optic line is run under ground from equipment to phone line. A RS-232 serial converter is on both ends of the fiber optic line. Its all Async RS-232. Modem talks just fine when connected directly with computer, add the serial converters in there though and all I get is garbage(not ASCII characters on the return from modem). The PLC dials out in the event of a fault via a RS-232 comport sending AT ASCII commands out to the modem. I am on the verge of simply saying run 1300feet of copper phone cord to the PLC and use the standard industrial modem already in the machine. But then I haven’t solved the problem. Is there any config problems between fiber optic RS232 and the RS-232? Right now I am stumped and looking for a fresh set of eyes. If you have any suggestions I would be extremely grateful. Even if you just say “WTF are your talking about this is a PLC forum, the weird backward technical imposibilties sections is two doors down take a left at the dancing pink elephants”. I am just throwing it out there, looking for a miracle. Thanks in advance.
George

Take a look here http://www.bb-elec.com/product_multi_family.asp?MultiFamilyId=85

About halfway down the page look at the diagrams. Is this what you are trying to do?

If so there are many device that do this but B&B stuff is pretty good and they have great support. IMO the price ain't bad.

You may be easier to buy a solution like this that is made to do just that and stop fighting with what you have IMHO.

Here is another http://www.moxa.com/product/ICF-1150.htm

Does that converter have a configuration to it? Could you be using the wrong baud rate,parity, stop bits,etc?

@jeff- Nope these converters are "supposed" to be plug and play Async fiber optic to serial port converters

(here is the link to the data sheet http://www.rs232-converters.com/converter_specs/232-fiber-mm.pdf)

@ The PLC Kid

Kinda like that, basiclly I am going DB9 from PLC, to converter, fiber optic to second converter, out of second converter DB9 and then into the modem. 62.5MM/125micrometer Fiber with ST 3m crimploc connectors.

The modem configuration seems to be the problem, something with the Flow control or Error correction. All I can tell you is that I don't know about the wall I am banging my head into, but I am getting pretty sore and frustrated. Thanks guys, hope to here from you again.

George

George,

Has this system worked in the past? Does your fiber optic converters provide 2-way communications, and do they use two fibers, one each for SEND and RECEIVE?

If so, one of the fiber paths (or converters) could be broken (probably the SEND fiber from the modem). Are there any spare fiber channels in the fiber cable? You might could switch to different one to fix the problem.

Hey guys sorry i didn't wrap up this post. Turned out to be a bad serial cable. I replaced it and bingo. System is working fine. Thanks for all your help.

You followed through that is all That matters