[Physics] Arguments for or against the variable time (of

[Doug Marett]

Hi Olivier,

  Well, some authors argue that the fiber optic cable in the gyroscope
drags the light around with it, so that there is a pro ported Fresnel drag.
See for example: https://ntrs.nasa.gov/search.jsp?R=19780065999
http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1021991
In reality, the effect of refractive index actually cancels out around the
fiber loop, so that the fringe shift detected is  independent of the
refractive index of the fiber. This was pointed out by Ruyong Wang here:
http://web.stcloudstate.edu/ruwang/PRL93.pdf - he considered that the fiber
optic gyro was different that the Fizeau experiment, since there is
co-movement between the source and the receiver in most arrangements. So
there are differing viewpoints on the matter.

Doug

On Tue, Nov 8, 2016 at 10:47 PM, O. Serret <o.serret at free.fr> wrote:

> Hi Doug,
>
> Sorry, I don’t understand what you mean.
>
> Sagnac effect is  dt = 4 Pi w R^2 / c^2
> It is explained by the fact the two photons do not travel the same distance
> In this case, there is no composition law for velocity
>
> Could you precise what you mean by “Fresnel drag does occurin the Fiber
> optic gyroscope” ?
>
> Thank you
>
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