[time-nuts] Frequency over fiber (was WWV and legal issues)

Tom Van Baak tvb at LeapSecond.com
Sun Sep 2 10:07:48 EDT 2018


> I suspect there’s a longer list of “slow” environmental effects that are also taken 
> care of with the compensation setup. One would guess that crossing a active  
> fault line would be “interesting”. 

Yes, here's a back of the envelope calculation for you:

- the Pacific Northwest moves on the order of 10 cm per year [1]
- 1 meter of time is 1/299792458 = 3.3 ns
- 10 cm/year is 3.3 ns / 86400 / 365 = 1e-17 df/f
- the best laboratory optical clocks are down to that level of stability [2]

On the other hand, in the real world you'd have to convince me that you've found two national timing labs with 1) state-of-the-art optical clocks, 2) which operate as phase (time) standards instead of as frequency standards, 3) or run continuously for a year (instead of a few times per week), 4) are connected by stabilized fiber, 5) that cross plate boundaries moving anywhere near as much as 10 cm/year, and 6) the optical time nuts running the clocks don't already factor geodetic effects like this into their clock comparisons...

Unfortunately I won't be able to measure this. Even if John Miles (who also lives near Seattle) and I find optical clocks on eBay some day, and we find a way to run 30 miles of fiber between us without anyone noticing, we are both on the same tectonic plate so the drift cancels out. Note that lunar/solar tidal effects would be common mode to us as well.

/tvb

[1]
https://pnsn.org/outreach/about-earthquakes/plate-tectonics
https://www.eoas.ubc.ca/courses/eosc256/jan26_plates_rebound.pdf

[2]
https://arxiv.org/ftp/arxiv/papers/1309/1309.1137.pdf
https://arxiv.org/ftp/arxiv/papers/1704/1704.06323.pdf
http://jilawww.colorado.edu/yelabs/sites/default/files/uploads/Sr%20best%20clock_Bloom_Nature.pdf




More information about the time-nuts mailing list