Thanks to all the posters. Especially to Dana -  That is exactly what I was 
looking for - suggestions for parts and/or circuits to do the job. I was 
originally thinking that I would go with a digital circuit (sine to square to 
sine), but maybe analog/sinewave would be simpler and perform about as well.

Anyway, I have ordered some of the recommended optical transceivers. We'll see 
how that works out.

One or two posters mentioned that phase noise and/or thermal stability may be 
issues. The referenced research papers don't seem to indicate that phase noise 
is a problem. I don't think that thermal effects will be a big problem for me - 
I just need to check the phase calibration from time to time. Certainly there 
are expensive commerical optical clock distribution systems with excellent 
properties. Maybe the devil is in the details... 

My specifical application at the moment is putting several SDRs at diverse 
antenna locs and feeding the IF via ethernet-converted-to-optical to my 
computer. I may want to transmit at some point but receiving is all I want to 
do for now. Still need a way to get a stable ref clock to each radio to provide 
phase coherence.... I only need 50-60 meters but an optical solution with 
single mode fibers can go many km if I ever wanted to scale up. Anyway, my plan 
is to have only power carried by copper.

I don't want to go with coax, twisted pair, or any other copper solution 
because of high ambient noise levels in my area and a desire to avoid adding to 
it. Stringing several 100 meters of copper about my yard, carrying 10 MHz clock 
signals, no matter if the cables are well shielded, doesn't seem like a great 
idea.

Overkill?  Probably.

BTW, I would NEVER try to do something like this with copper Ethernet. Even 
shielded Ethernet cables (Cat-7 and Cat-8) radiate badly when used for 1-G and 
10-G Ethernet.

Thanks again to all!

Jim
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