On 04/03/2012 01:10 PM, Jim Lux wrote:
On 4/3/12 12:49 AM, Azelio Boriani wrote:
Yes, but nonetheless why not develop more stable primary clock
sources? We
can always take care of the dissemination in the meantime and try to
develop a more precise time transfer method.
On Tue, Apr 3, 2012 at 2:39 AM, beale<[email protected]> wrote:
Having read this NIST review paper by Thomas E. Parker, "The uncertainty
in the realization and dissemination
of the SI second from a systems point of view"
http://tf.boulder.nist.gov/general/pdf/2564.pdf
...it seems that any potential improvement in frequency standards (Cs
fountain -> optical clocks) will not benefit most time/frequency users,
because existing long-range time-transfer methods (TWSTFT and GPS
carrier
phase) are still limited to at best 2E-16 for 30-day averaging, and
there
is no generally practical way to improve them currently in sight. (Laser
ranging of satellites being considered not generally practical). Just
curious what people think, is this too pessimistic a view, or is it
fair to
say that having a 10x improved primary standard would not improve
stability
or accuracy for anyone outside of stabilized optical-fiber distance from
such a standard?
In general, as a technology developer, I agree with you, but the sources
of money with which to develop technology often have a slightly
different view.
I wonder if they have really reached the measurement limit possible in
fibre systems.
If one is serious about pushing fibre based TT systems down, there is a
number of techniques one could apply as an ensemble, but I have not seen
any serious work, only working on different pieces of the puzzle.
Hence, I think the article may be premature in this respect.
Cheers,
Magnus
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