[time-nuts] Fw: Optical transfer of time and frequency

[Magnus Danielson]

If the dynamics is working for you, yes, you can use something like 
that. If you have noise, you would like a spreading code such that the 
correlation in the receiver suppress the noise.

MVH
Magnus

On 05/02/2016 11:14 AM, Michael Wouters wrote:
> One other possibility occurs to me that might be doable with surplus
> gear and sticks to the  budget. Instead of using WR, give up on
> getting time of day and just send a 1 kHz pulse stream in each
> direction. Each station then measures against its own GPSDO clock
> using a standard/homebrew TIC and records the difference. This is
> ambiguous modulo 1 ms but this is trivially resolved using GPS. You
> also probably know the distance between the stations to much better
> than 1 ms = 300 km :-) . You then post-process but this can be done
> with very little latency if you're keen.
>
> Cheers
> Michael
>
> On Mon, May 2, 2016 at 1:44 AM, Tom Van Baak <tvb at leapsecond.com> wrote:
>>> Has anybody experienced with free-space optical gigabit Ethernet
>>> links? I am curious about whether the transceivers have a fixed
>>> latency or at least a latency one can easily quantify online. This is
>>> the trickiest part for adding WR support on top of a given physical
>>> layer.
>>
>> Hi Javier,
>>
>> When searching this topic I ran across a commercial laser solution:
>>
>> http://www.laseroptronics.com/products.cfm/product/27-0-0.htm
>> http://www.laseroptronics.com/index.cfm/id/57-66.htm
>> http://www.laseroptronics.com/index.cfm/id/57-69.htm
>> etc.
>>
>> But, according to /57-67.htm it "starts" at $15k per node. Plus there's the cost of all the WR pieces, assuming the two are even compatible. So this is vastly above the ~$2k budget mentioned by OP. I also assume OP is not ready to embark on a one-off, multi-man-year R&D project.
>>
>> This particular issue -- how to synchronize (or, at least phase compare) multiple oscillators by a two-way laser link over a few km to within 500 ps -- is really quite interesting. It would, for example, allow me to do live monitoring of 5071A Cs time dilation on my next mountain-valley relativity experiment.
>>
>> /tvb
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