Hello;

My experience with Profibus fiber-optic communications has been limited to Siemens OLM modules. I am not familiar with Moxa media converters. 

What model of Mioxa media converter are you using, and which type of fiber have you installed? What is the distance between the CP 443-5 and the end-station? What diagnostic signals is the media converter giving you for your setup?

Moxa has always provided us with excellent support on their equipment, and they should be able to analyze your topology if you provide them with enough information. I suggest you try to contact them on this installation.

https://www.moxa.com/en/support

Hope this helps,

Daniel Chartier

Hello,

I can only point you to Moxa PDF on Moxa site (external PDF): Moxa ICF-1180 info

There are infos about diagnostic procedure, what you need to do to diagnostic your network, use of some Moxa tools and other options. Did you tried that? On other side in this case you can also check Profibus options inside defined S7 PB DP cfg, there are also other settings about devices used on bus, what options you can set and take to account about existing options on bus, also what PB DP option is set - Profibus DP/Standard/FMS/User defined. here maybe I would try Standard option because probably no default Siemens devices are on bus, only idea for tests.