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<DIV>Hi Doug,</DIV>
<DIV> </DIV>
<DIV>Thank you for your answer. According to this paper, air core fiber
propagate light at very close to the vacuum speed of light. But which speed
?</DIV>
<DIV> </DIV>
<DIV>My understanding is air core principle is different from the silica core
principle : </DIV>
<DIV>- air core is based on REFLECTION, </DIV>
<DIV>- silica core is based on REFRACTION. </DIV>
<DIV>Is it correct ?</DIV>
<DIV> </DIV>
<DIV>In this case, due to multiple reflections, “linear” or average speed of
light in air core would be lower than expected (<FONT face="Times New Roman">the
"linear" photon speed in the fibre optic cable would be </FONT><FONT
face="Times New Roman">a reduction of about 30%,</FONT> according to <A
title=http://physics.stackexchange.com/questions/80043/how-fast-does-light-travel-through-a-fibre-optic-cable
href="http://physics.stackexchange.com/questions/80043/how-fast-does-light-travel-through-a-fibre-optic-cable">http://physics.stackexchange.com/questions/80043/how-fast-does-light-travel-through-a-fibre-optic-cable</A>)</DIV>
<DIV> </DIV>
<DIV>In silica core, due to the refraction, speed of light is (1/1,5=) –30%
lower than vacuum speed of light if light goes approximatly in a straight
way.</DIV>
<DIV> </DIV>
<DIV>So I precize my question : </DIV>
<DIV> </DIV>
<DIV><STRONG><FONT face="Courier New"><I style="WHITE-SPACE: pre">Since 2004, do
you know if “LINEAR” celerity of light in an air core fiber and in a silica core
have</I></FONT><I style="WHITE-SPACE: pre"><FONT face="Courier New"> been
measured ?</FONT></I></STRONG></DIV>
<DIV><EM><FONT face="Courier New"></FONT></EM> </DIV>
<DIV><FONT face="Courier New"><FONT face=Calibri>Thank you</FONT> </FONT></DIV>
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