[time-nuts] Optical transfer of time and frequency

[Magnus Danielson]

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.

The two-way time-transfer is relatively easy, but you will need to do 
some calibration to get the precision needed.

Now, what is the needed precision?

Why can't you pull fiber?

Still wonder how you use the time, to understand the timing requirements.

Cheers,
Magnus

On 04/29/2016 08:50 PM, Ilia Platone wrote:
> There is line of sight.
>
> The budget is around 2k€ by now, but can be increased.
>
> This project is for an amateur astro club, and the resources they would
> give to me are limited, except the place where to do this and some optics.
>
> The setup must be mobile, I mean that I should be able to place the
> telescopes in other places "easily".
>
> There is some material however. Material includes FPGA boards, VOCXO +
> PLL boards, IR lasers and APD sensor boards, ARM boards, and consumer PCs.
>
> There is also the possibility to use some optics like small reflector
> telescopes, as pointed before, they could be used as beam expanders for
> IR lasers.
>
> Ilia.
>
>
> Il 29/04/2016 09:36, Michael Wouters ha scritto:
>> On Fri, Apr 29, 2016 at 1:18 PM, Bruce Griffiths
>> <bruce.griffiths at xtra.co.nz> wrote:
>>> Quoting Michael Wouters: "According to this,
>>>
>>> http://www.nist.gov/manuscript-publication-search.cfm?pub_id=912449
>>>
>>> there are many practical challenges  with a one way free-space
>>> optical link."
>>> That paper indicates that  one way transfer with noise of a few
>>> picosec should be feasible using an IR laser.
>> Oh, yes I see in Fig 2b that the short term, one-way noise is ca. +/-
>> 5 ps. And probably with temperature measurements, the long term
>> variation could be compensated.
>>
>> But we still don't know if there is line of sight.
>>
>> Cheers
>> Michael
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>