ControlNet Fiber Repeater

Hi All,

Is there any special configuration needed to apply when using a Fiber Repeater for ControlNet?
I have a ControlLogix L61 (v16) running with a 1756-CNBR to communicate with a 1734-ACNR (no other node). It works when I connect direcly from the CNBR to the ACNR via coaxial cable only. But when I add a pair of fiber repeater in between, it doesn't work.
The fiber repeater is 1786-RPA + 1786-RPFRL, I'm using ST patch cable and had Tx connecter on one repeater connected to Rx connecter on the other repeater.
I would like to test the fiber cable but I don't have a tester on hand.

Appreciate any suggestion. Thank you!

There are network timing adjustments for the physical layer in RSNetworx for ControlNet, to allow for very long co-ax runs or the use of fiber repeaters.

I don't have the software in front of me, but the basic idea is that you tell RSNetworx how much co-ax cable and how many repeaters are in the ControlNet trunk. I think that Network Properties are in a pull-down menu.


In general, one pair of 1786 repeaters will work with default network timing, which is why I think the problem is probably a damaged or mis-terminated fiber.

Hi Ken,

Thank you for your fast reply!
The NUT is setting at 5ms (default). I'm suspecting the repeater is damaged rather than the fiber as it is relatively "older" compare to the fiber cable.
Sadly I don't have a new repeater nor a fiber tester to replace or test to find out. Thanks again.

It's more than the NUT timing; these are low-level "skew" and "guardband" values that the programmers never see and are baked into the scheduling algorithm. Usually you just tell RSNetworx that there is a pair of repeaters, and it takes care of the rest.

Unfortunately with those RPFRL repeaters, they run at 1300 nm wavelength which is infrared, not visible red light. You might be able to see it with a CMOS camera like in a cell phone or webcam, if you can't get your hands on a fiber tester.

Thank you Ken. You are right. I didn't add those repeater modules in RSNetworx.
Unfortunately, it still doesn't work after I added and re-schedule the netwrok (it works without the repeaters in between, though).
I will see if I can get a fiber tester to test the RPFRLs and cables.