I am going to withdraw statement 3). It is a waveguide result which I now
do not think applies to fiber optics. Still thinking and looking : )
Bob Sciamanda
Physics, Edinboro Univ of PA (Em) http://www.winbeam.com/~trebor/
trebor@winbeam.com
----- Original Message -----
From: "Bob Sciamanda" <trebor@WINBEAM.COM>
To: <PHYS-L@LISTS.NAU.EDU>
Sent: Wednesday, February 16, 2005 3:51 PM
Subject: Re: Travel distance in a waveguide.
| Perhaps this summary will help:
|
| 1) In a "step-index" fiber, the wave number B in the resultant wave
| E(r)=f(r)exp(i(Bz-wt)) is constrained to:
| (n2)k = k2<= B<=k1=(n1)k, where
| k is the vacuum wave number, n2 is the clad index and n1 is the core
index.
| Thus the fiber phase velocity always "lies" between the bulk phase
| velocities v1 and v2 (n1 and n2 typically vary by less than a few
percent).
|
| 2) In a typical graded index fiber, where n(r) goes, via a power law in
| (r), from a value n1(at r=0) to a final (cladding) value n2, B => n2.
|
| 3) In both cases, the product of the phase and group velocities = c^2.
|
|
| Bob Sciamanda
| Physics, Edinboro Univ of PA (Em)
| http://www.winbeam.com/~trebor/
| trebor@winbeam.com
| ----- Original Message -----
| From: "Edmiston, Mike" <edmiston@BLUFFTON.EDU>
| To: <PHYS-L@LISTS.NAU.EDU>
| Sent: Monday, February 14, 2005 9:59 AM
| Subject: Re: Travel distance in a waveguide.
|| . . .
|| How would the group refractive index measured for a step-index fiber
|| optic cable compare to the refractive index measured for the bulk
|| material using a prism in a spectrometer or using a flat hunk of the
|| material in an Abbe refractometer (critical-angle technique)?
|| . . .|
|| Michael D. Edmiston, Ph.D.
|| Professor of Chemistry and Physics
|| Bluffton University
|| Bluffton, OH 45817
|| (419)-358-3270
|| edmiston@bluffton.edu
||
||
|
|