Elenco Fiber Optics Voice Data Kit - Manual (Page 22)

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Fiber optics was first used for communications in 1976
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In previous experiments you worked with short fiber optic bundles that transmitted a coherent
image. We used a short length only as a matter for your convenience. One of fiber optics' greatest
benefits is its ability to function over very long distances. The 3 mm diameter coherent rod you
experimented with previously was originally 1.2 meters (48 inches) long, from the manufacturer. In
this experiment you are going to construct a much longer bundle, which will also be flexible.
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Penlight with batteries
25 .25 mm (.01 inches) unjacketed optical fibers, 1 m (39.4 inches) long
5 mm (3/16 inch) diameter white heat shrink tubing, 7.5 cm (3 inches) long
Rubber bands (3)
Single-edge razor blade or sharp knife*
Blow dryer*
* Not contianed in this kit.
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• Using a sharp knife or razor blade, cut all the .25 mm (.01 inch) diameter fibers into 30 cm (9
inch) lengths.
• Insert all of the .25 mm fibers in the heat shrink tubing. Arrange the fibers so about 1.5 cm (3/8
inch) of the fiber ends sticks out beyond one end of the heat shrink, and fibers are flush with
each other. Hold fibers in place with the rubber bands.
• Once all the fibers are in place, heat the shrink tubing with a blow dryer to contract the tubing.
Use heat sparingly to avoid damaging fibers.
• Trim both ends of the fiber so they are all the same length, using a razor blade or sharp knife.
• Turn the penlight on. (Remove the rubber boot if it is installed.) Hold the bulb end of the
penlight against the exposed tips at either end of the fiber bundle and observe the light coming
out the other end.
• Bend the fiber bundle while holding one end to the penlight's bulb.
• Point either end of the fiber bundle toward the sun while flexing the bundle.
• Place either fiber end over the text on this page while viewing the tips at the other end.
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The fiber bundle that you assembled is flexible
and will readily transmit light from one end to the
other when one end is pointed at the penlight bulb.
No changes in light intensity should occur as you bend
the bundle, provided you keep the fiber tips and
penlight in the same positions. Light from the sun will
also travel from one end to the other, and will not
vary as you move the bundle. This bundle will not
transmit an image of the text because the fibers are not precisely aligned with each other on both ends,
although as you move the bundle across the text you may notice some fibers going from white to
black. This collection of optical fibers is flexible, but it is an incoherent bundle.
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As you may have seen in the news, an important use of fiber optics is for telephone
communications. In telephone applications its long distance capability is being widely used to transmit
large amounts of information. Fiber systems have been laid across the Pacific and Atlantic oceans. A
link already in operation stretches from Long Island, New York, to Lands End, Britain, to Penmarch,
France.
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