[time-nuts] time-nuts Digest, Vol 86, Issue 89

[Colby Gutierrez-Kraybill]

> Message: 6
> Date: Sun, 25 Sep 2011 15:41:03 -0700
> From: Jim Lux <jimlux at earthlink.net>
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] Fast than light neutrino
> Message-ID: <4E7FADFF.20204 at earthlink.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> On 9/25/11 3:26 PM, Hal Murray wrote:
>> 
>> javier.serrano.pareja at gmail.com said:
>>>> A fiber-based time-transfer would be nice complementary as it would provide
>>>> an independent timing path.
>>> Any ideas on how to proceed? This is unknown territory for me.
>> 
>> You can get a lot of good ideas from the radio astronomers.  It's been
>> discussed here in the past, but I don't know what terms to use when searching
>> the archives.  I think it was mostly pointers to their papers.  They were
>> interested is much shorter distances.  I think it was 10-20 km.
>> 
>> 
>> The idea is to send a signal in both directions over the same fiber.  If it's
>> the same fiber, the transit times are likely to be the same in both
>> directions.  If you send a pulse out and back, you can assume the time the
>> pulse arrived at the far end was half the round trip time after it left the
>> start.
>> 
>> 
>> Whatever you do, it will require a lot of cooperation from the people who own
>> the fibers.
>> 
> 
> The Deep Space Network do lots of this kind of thing for interferometry.
> 
> 

Normally this is accomplished by using maser clocks, usually locked to a GPS PPS.

- Colby