On Sat, Apr 30, 2016 at 6:14 AM, Magnus Danielson <mag...@rubidium.dyndns.org> wrote: > Well, giving the conditions mentioned, doing ranging codes such as those > used by GPS is very easy and cheap. Doing this in bidirectional isn't too > hard. Doing a suitably high chip-rate should cost very little.
I've done two-way time-transfer over optical fibre using exactly this technique. The TDEV is about 1 ps for tau>1s. Not so cheap, about 25K euro per node (20K signal processing - NI FPGA, 2K laser and power supplies, 1K detector, 1K RF electronics) in my setup, but that cost could be greatly reduced since a $100 OEM FPGA could do the signal processing (I've already done work on this but currently looking for motivation to finish it off) and a simple, intensity-modulated laser would probably be fine. A 2K euro budget would be a challenge though. > The two-way time-transfer is relatively easy, but you will need to do some > calibration to get the precision needed. > At first glance, I would think that you should be able to define the optical RX/TX path to within 10 cm without any trouble and that gives you 300 ps accuracy. Even on fibre links, I don't think anyone would claim an accuracy of better than a few hundred ps. Cheers Michael _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.