On Apr 17, 12:33 am, Richard Clark wrote:
On 16 Apr 2007 17:50:10 -0700, "K7ITM" wrote:
....
I still
don't have a reference that a fiber optic cable is a TEM transmission
line, though I have others that say that it's not.

That example of the non-TEM fiber optic would be rare species indeed.
I've seen them, but that hardly constitutes the sole species of the
breed.

So give me a reference already. I find lots of references, including
ones that explain the propagation, that talk about TM, TE, hybrid, and
even quasi-TEM mode propagation in a fiber. What boundary conditions
are there in an optical fiber that give TEM mode?


I still don't have
information on whether a soliton wave can propagate in a linear
medium, though I have references that say it is a non-linear
phenomenon that occurs in non-linear media.

Of course it can propagate in a linear medium. Solitons were first
reported in linear media - water - something like one hundred seventy
years ago.

Solitons can induce non-linearity in otherwise linear
media. Solitons also interact in collision with a phase shift
afterwards. Solitons have been applied to data transmission in fiber
optics for a dozen years or more.

Your references are pretty sparse.

Yours seem non-existent. Mine at least did a good job explaining the
phenomena.

From Wikipedia, for example, about solitons:
"The stability of solitons stems from the delicate balance of
"nonlinearity" and "dispersion" in the model equations. Nonlinearity
drives a solitary wave to concentrate further; dispersion is the
effect to spread such a localized wave. If one of these two competing
effects is lost, solitons become unstable and, eventually, cease to
exist. In this respect, solitons are completely different from "linear
waves" like sinusoidal waves. In fact, sinusoidal waves are rather
unstable in some model equations of soliton phenomena. Computer
simulations show that they soon break into a train of solitons."

There is specific mention of the Kerr effect--a nonlinearity in
optical media that support soliton transmission. One of the
references I saw specifically said that solitons are solutions to non-
linear differential equations. Since the equations governing the
behaviour of waves derive from the properties of the propagation
medium, I expect that any medium that can propagate a soliton is
nonlinear. Another reference specifically addressed the nonlinearity
of water as a transmission medium, as a necessary part of its being
able to propagate solitons.



If you can convince me
that a wavefront coming to a Magic T doesn't see it as an impedance
discontinuity, we could perhaps post more about that--or not.

Consult Terman. He is quite compelling when it comes to describing
microwave plumbing. This hardly constitutes more than 4 pages total
reading, if you choose to move on beyond the first page of discussion.

I find nothing in the index of my "Radio Engineers' Handbook" by
Terman under either "Magic" or "Hybrid". Sorry. The three different
coaxial "Magic T" hybrid designs I DID find all do show an impedance
discontinuity: the junction of more than two lines of equal impedance
and/or impedance steps in through-lines. Sorry.

Time to move on.

Cheers,
Tom