I am playing with a couple of Trendnets, also in single mode; it's my first real experience of optical in my own system and I like what they do.Makes sense. I just tried a pair of TrendNet FMCs with TrendNet single-mode SFPs, just to test the impact of optical on my system. The results were very positive.
As an aside, even the designer of my DAC (the technical Grammy-award winning Daniel Weiss), had suggested to me that noise over ethernet shouldn't be an issue and measures to isolate it shouldn't be needed. He referred to the fact that ethernet connections are galvanically isolated by design.
I still have my Pink Faun LAN isolator in the chain, after the FMCs. Maybe it is serving to clean up any noise the SFPs produce, as you suggest. At the least, it doesn't do any harm.
Next stop will be the Fiberbox II (in a couple of months).
All DAC designers claim you don't need any of this add-on stuff (switches, FMC's) to hear their DAC at its best, and most who supply their DACs with switched mode PSU would claim the same! Galvanic isolation is a mitigator not a neutraliser. If galvanic isolation was all we needed, any cheap ethernet switch would do the job as galvanic isolation is basically inherent in network switch board designs. But clearly we audiophiles go further than that, and it's not just because we have wild imaginations.