Anybody gone from ethernet to optical for connection to a streamer?

Appreciate use of word renderer indescribing the streaming foodchain.

I have both (wired ethernet and fiber).  Fiber is clearly superior.

I have an Etheregen and tried it with both Fiber and CAT and I could not hear the difference. (yes, I had only one hooked up at a time).  The Etheregen switch claims it's "moat" galvanically separates the "in" from the "out". My limited listening test confirmed this in my opinion. That said, I don't know if this helps answer your question, but you might find it useful.  

I’m a little confused are you talking about a fiber connection from your modem/ router to a streamer. If so what type of modem? I’m in the telecom industry but not familiar with any modem that that has fiber outputs only a single input. What equipment is before the streamer?

I can't speak to the optical portion of your question here - but I do know I swapped out my normal, everyday ethernet cable with an "audiophile grade" CAT 7 cable from Pangea. And it introduced the absolute worst ground loop/ hum into my system that I have ever had. (And, I'm still confused about how that happened... I can repeat this, and tried two different cables from them with the same results if anyone is interested.) The optical connection has the potential of reducing ground loop issues, but if you can't hear a hum/ buzz now, it most likely won't make much of a difference.