Re: ATM Fiber light source - a burning issue

[Brad <brad@escapees.com>]

I had been thinking about a "artificial star" for testing but didn't think
about fiber optics.  I wonder if a 1mm ball would be needed?  Remember the
old fiber optic lights which were marketed about the same time as lava
lamps?  Multiple strands of fiber optics which draped down like the
branches of a weeping willow tree. I doubt if each end was terminated in a
ball, but maybe they were.  Each end was brightly illuminated in a point of
light.  I've got access to some fiber optic jumpers, guess I'll do some
experimenting.

Brad


On Mon, 16 Oct 2000 19:46:58 -0400, you wrote:

>
>Hi:
>       I ran into a problem with making a point light source.  I wonder if anyone 
>on the list can help.
>         A bright point light source is almost always needed for optical 
>testing - Foucault, Ronchi, interferometer, etc.  I was therefore 
>interested in coming across a 1978 paper on how to make an inexpensive, 
>very bright pinhole source from fiber optics.  The paper, by R.E. Parks and 
>R.E. Sumner (Applied Optics 17(16), 2469, 1978), suggests getting a 10" 
>piece of fiber optic, then melting one end into a 1mm diameter ball with a 
>propane torch.  When a laser or microscope illuminator is applied to the 
>other end, the ball end becomes a brilliant point source with well over 180 
>degrees solid cone angle.
>       The authors used an Edmund Scientific #2516 fiber.  The current Edmund 
>catalog doesn't list that item anymore or anything similar, as far as I can 
>see.  The closest item is a bundle of 12,500 glass fibers for about 
>$51.00.  Since I only need a fiber or two, I thought I'd scrounge around.
>       A thought occurred to me that modern computer networks use fiber 
>optics.  My friendly computer tech gave me two feet of TCP/IP cabling.  I 
>striped the various layers of jacketing and got four pieces of thin, 
>flexible material with a white plastic sheathing.  I took out a propane 
>torch and, as expected, the burned off the plastic.  What's left looked 
>like thin glass.  It turned red and bent when heated, but no melting and no 
>balling up.  It also snapped off easily.
>       My question is, what did I do wrong?   Was I mistaken in assuming that the 
>authors used glass fiber, not plastic?  Is a propane torch in fact hot 
>enough to melt a thin glass strand?
>       Thanks everyone.
>
>P.C. Chen 
>