Take a look at what these guys sell. Not too expensive and it works great. I have a few OpticalRendu's using their accessories.
@brylandgoodman This is what I use for my two systems and it works great. Lps is optional but better than wall warts. Small green computers is excellent but more expensive if that matters. I own their sonic transporter it is fantastic.
I can't really figure out what he is trying to do... not sure why he isn't plugging the ethernet cable into the modem and the modem into the computer. There are multiple programs you can work with directly on your computer once they get there that should do whatever it is he wants to do and unless I missed something, a lot simpler.
Back up first and be sure everything works in copper. Any old dirt cheap CAT-5 cable will do. Actually it will do as well as any snake oil "audio Ethernet" cable. Ethernet and TCP guarantee every bit is right. Everything is buffered so no magic timing differences.
Then test/listen to the system and see if you have a problem in the first place before you add band-aids for problem that does not exist or think you can magically get sonic improvements. You won't within the laws of physics in this universe. I know, some here seem to be in another universe with different laws where the IP stack is analog.
Optical transceivers should be totally transparent to the computer/router/switch etc ports. They just convert bits to bits and do nothing to the protocol, unless newer venders have found ways to screw things up. The transceivers we used were st connections for multimode fiber and did 1G E. I can't remember the brand but they were cheap and reliable. Grey box. Multimode and single mode fiber are not interchangeable.
I do not understand why an "active" optical cable and also list transceivers. You should just need an SPF cable.