[time-nuts] About 10 MHz Optical Distro

[AC0XU (Jim)]

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