Elenco Fiber Optics Voice Data Kit - Manual (Page 20)

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Sand (silica) melts to form glass at approximately 2000
°C
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The 3 mm (1/8 inch) diameter image conduit used in previous experiments is made of glass. As
you know, glass can be formed into many different shapes. Windows are flat, bowls and dishes are
curved, and more complex shapes are used in the test tubes and flasks found in a chemical laboratory.
We will show you how to change the shape of this glass image conduit to illustrate one of the
important capabilities of coherent image guides.
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3 mm diameter × 4.3 cm (1/8 × 1-3/4 inch) image conduit (glass-like rod)
2 small binding clips
Isopropyl alcohol*
Paper towels*
Cotton gloves or two pads of cloth*
Alcohol lamp, Bunsen burner or propane torch*
* Not contained in this kit.
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• Clean the image conduit with isopropyl alcohol and a paper towel. Attach a paper binding clip to
each end of the image conduit. Light your heat source and let its heat stabilize. Make sure it rests
on a steady surface. Put on gloves or have two pads of cloth handy.
• Hold the image conduit, using the binding clips, with gloved hands
or pads of cloth. Position the conduit's mid-section at the very tip
of the blue flame for about 30 seconds. Remove from the heat and
let cool for five minutes. Remove binding clips and see if the image
conduit kept its image transmission properties by placing either
end over the printed text on this page and viewing from the top.
• Place the binding clips again onto the image conduit and back into
the flame while turning it slowly. Continue heating the mid-
section until it starts to soften. Using both pads and light pressure,
bend the conduit 45 degrees from vertical as shown in the figure.
Turn off the heat source and let the conduit cool for five minutes.
• Place one end of the image conduit over the text on this page
while looking into the other end. Move the conduit to different
letters on this page. Has bending changed its image-transferring
properties?
R R R R EEEE SSSS UU U U LLLL TTTT SSSS ::::
Heating the center of the image conduit until it grew hot, then letting it cool, did not affect its
image transmission properties, nor did heating and bending it at an angle. After the light guide was
bent it transferred an image just as it did when straight. The experiment shows that fiber bundles will
transmit images through bends and around corners.
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The fiber optic light guide is composed of thousands of individual glass fibers. Each fiber consists
of a central light-carrying portion and outer cladding. Heating the image guide does not melt the core
and cladding together (which would make it lose its image-transferring properties). The heat only
makes it flexible enough to form into a new shape.
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The addition of various metallic compounds can produce different colors in glass. Addition of
Cobalt oxide produces blue glass. Green glass is obtained by adding chromium or iron compounds.
Red glass is produced by adding cadmium, cuprous oxide, or gold. In the making of optical fiber,
manufacturers strive the reverse: they try to remove as many impurities as possible.
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