<div dir="ltr"><div><div><div>Hi Olivier,<br><br></div> I did find this article here: <a href="http://www.extremetech.com/computing/151498-researchers-create-fiber-network-that-operates-at-99-7-speed-of-light-smashes-speed-and-latency-records">http://www.extremetech.com/computing/151498-researchers-create-fiber-network-that-operates-at-99-7-speed-of-light-smashes-speed-and-latency-records</a><br></div>which seems to suggest that air core fiber experiences a lot of signal loss, but can propagate light at very close to the vacuum speed of light. <br><br></div>Doug<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Nov 11, 2016 at 5:45 PM, O. Serret <span dir="ltr"><<a href="mailto:o.serret@free.fr" target="_blank">o.serret@free.fr</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">
<div dir="ltr">
<div style="FONT-SIZE:12pt;FONT-FAMILY:'Calibri';COLOR:#000000">
<div>Hi Doug,</div>
<div> </div>
<div><font face="Courier New">> <em>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: </em></font><a style="white-space:pre-wrap" href="http://web.stcloudstate.edu/ruwang/PRL93.pdf" target="_blank"><font face="Courier New"><em>http://web.stcloudstate.edu/<wbr>ruwang/PRL93.pdf</em></font></a><font face="Courier New"><em> </em></font></div>
<div><em><font face="Courier New"></font></em> </div>
<div> </div>
<div>This article of 2004 is very interesting, but quite difficult to understand
for me. They used an air core fiber. Because it is air, it is suggested that the
refractive indice would be = 1, and so the celerity of light in the fiber would
be the celerity of light in vacuum. I’ve checked on internet, and I only found
an “equivalent” index consitent with the definition of the Numerical Aperture
(?). My question is :</div>
<div> </div>
<div>Since 2004, do you know if celerity of light in an air core fiber has
been measured ?</div>
<div> </div>
<div><font face="Courier New"><font face="Calibri">Thank you </font></font><font face="Calibri">for your help</font></div></div></div></div>
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