[time-nuts] Optical link connects atomic clocks over 1400 km of fibre

David davidwhess at gmail.com
Tue Aug 23 18:11:37 EDT 2016

I could not find it in the links but Magnus mentions 50 Hz instead of
100 Hz.

I would expect a 100 Hz noise signal if it was vibration coupled from
magnetostriction in a transformer; magnetostrictive strain depends on
the magnitude of the magnetic field strength and not the sign which is
why 50/60 Hz transformers hum at 100/120 Hz.  50 Hz however fits with
piezomagnetism if the optical fiber was in an oscillating magnetic
field and antiferromagnetic; for piezomagnetism, the strain does
follow the sign.


I do not know if optical fibers are even slightly antiferromagnetic
but maybe doping can make them susceptible?

On Wed, 24 Aug 2016 09:31:57 +1200, you wrote:

>What is the coupling mechanism giving rise to the 50Hz disturbance?
>DaveB, NZ
>----- Original Message ----- 
>From: "Magnus Danielson" <magnus at rubidium.dyndns.org>
>To: <time-nuts at febo.com>
>Cc: <magnus at rubidium.se>
>Sent: Wednesday, August 24, 2016 8:54 AM
>Subject: Re: [time-nuts] Optical link connects atomic clocks over 1400 km of 
>> ...
>> These links is in principle not very complex, but they are regardless 
>> somewhat sensitive. One link experienced excessive 50 Hz disturbance, 
>> which they could trace to the fact that for a short distance the fibre was 
>> laying alongside the house 400V three-phase feed-cable with quite a bit of 
>> current in it.
>> ...
>> Cheers,
>> Magnus

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