[time-nuts] Fast than light neutrino

pablo alvarez pabloalvarezsanchez at gmail.com
Mon Sep 26 17:17:47 UTC 2011


Hi guys,

Here you have the reports on the CERN's timing chain.

http://www.ohwr.org/documents/111

Questions are welcome!

pablo

On Mon, Sep 26, 2011 at 2:46 PM, Joe Gwinn <joegwinn at comcast.net> wrote:

> At 6:56 AM +0000 9/26/11, time-nuts-request at febo.com wrote: (really Javier
> S)
>
>> Date: Mon, 26 Sep 2011 08:56:12 +0200
>> From: Javier Serrano <javier.serrano.pareja at gmail.**com<javier.serrano.pareja at gmail.com>
>> >
>>
>> To: Discussion of precise time and frequency measurement
>>        <time-nuts at febo.com>
>> Subject: Re: [time-nuts] Fast than light neutrino
>> Message-ID:
>>        <CAHBYzfTSx=**jMKg218Sy6F9ji93OAht2=60w9_**
>> YY74-G-bkHGEA at mail.gmail.com <60w9_YY74-G-bkHGEA at mail.gmail.com>>
>> Content-Type: text/plain; charset=ISO-8859-1
>>
>> [snip]
>>  >
>>
>>>
>>>  I did not express myself correctly. We know how to do accurate two-way
>> sync
>> over a few km of fiber. See e.g.
>> http://dl.dropbox.com/u/**13409775/pac2011/WEOAN1.pdf<http://dl.dropbox.com/u/13409775/pac2011/WEOAN1.pdf>or
>> http://dl.dropbox.com/u/**13409775/wrapper.pdf<http://dl.dropbox.com/u/13409775/wrapper.pdf>(our contribution to the CLIC
>> Conceptual Design Report).
>>
>
> Thanks for the reports.
>
>
>  What is new for us is going through more than
>> 1000 km of fiber (only neutrinos have the luxury of going in a straight
>> line
>> through the crust of the Earth, 732 km). I wonder who one calls for fibers
>> and also more technical things like optical amplifier technology with
>> typical ranges, etc. What I gather from the discussion so far is that 100
>> km
>> is within reach of available optical transceivers. I wonder how far one
>> can
>> go with EDFAs.
>>
>
> EDFAs can easily achieve 10 dB or running closer to the edge 20 dB of gain,
> all with no electronics delay, but EDFAs are quite noisy, so there is a
> tradeoff to be made.
>
> EDFAs are inherently bidirectional, although they usually contain an
> optical circulator to make them unilateral.  But it would not be hard to
> make EDFAs that amplified in one direction for one wavelength, and in the
> opposite direction at a different (but nearby) wavelength.
>
> And one can also have a command wavelength, to allow for commanding of
> direction reversals and the like, so the fiber companies involvement is
> limited to hosting and installation of equipment.
>
>
>  One thing we could do is establish a fiber link between METAS
>> in Bern and CERN, and then look for a good metrology place in Rome (the
>> national one in Italy is in Torino I believe) and have a link between them
>> and Gran Sasso. Then we could use their UTC data sets to establish a paper
>> link between CERN and Gran Sasso which would be independent of the current
>> link.
>>
>
> Why do all that, versus just running an amplified fiber between CERN and
> Gran Sasso?  Two links are likely to be twice the trouble and error.
>
>
> Joe Gwinn
>
>
>
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