Convert mode on the fibreACE card was designed for use between a dLive MixRack and Surface, with both ends equipped with fibreACE. Theoretically, you can have a fibreACE card on one side only, and a third party converter on the other (for example for connecting to a GX4816 or an SLink port), like suggested above, but you would need to match the transfer rate and fibre mode of the fibreACE card as not all converters and SFP modules work the same way.
Typically for these applications, converters are always bought in pairs, with the same specs and performance on both sides of the fibre. So I would say that a pair of third party CAT-fibre converters is the way to go for the scenarios described above.