Elenco Fiber Optics Voice Data Kit - Manual (Page 25)

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Optical fibers, although very pure, are not crystals
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A crystal is commonly considered a solid object with flat sides
and sharp corners in a symmetrical arrangement. One example is rock
salt, which has an atomic structure as shown. Such materials always
break cleanly along specific lines and patterns like diamonds or rubies.
Now we will experiment to learn about the structure of Ulexite, glass
and plastic fiber.
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Ulexite
2 mm unjacketed optical fiber, 50 cm (20 inches) long
3 mm diameter × 4.3 cm (1/8 ×1-3/4 inch) image conduit
(glass-looking rod)
Three-sided file (a small emery board for fingernails will also
work)*
Pliers*
* Not contained in this kit.
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• Scratch a nick in the cladding of the plastic fiber about 12 mm (.5 inches) from one end with one
of the file's (emery board) corners.
• Select a spot near one end of the image conduit where the fiber bundle is not twisted and scratch
it with the file in the same manner.
• Scratch a line on one of the Ulexite's flat viewing
surfaces with the one of the file's corners.
• Position the plastic fiber on a table so the nick faces up,
and the nick portion slightly extended from the table
edge. Press down firmly on the main part of the fiber
with one hand (close to the nick) and grip the end of the
short half-inch section with thumb and forefinger of your
other hand. Now break off the short piece as you would
break a cracker.
• In the same fashion, break the shorter piece off the glass
image guide.
• Grip the Ulexite squarely with a pair of pliers on one
side of the scratch. Grasp the other side with thumb and forefinger, then snap the Ulexite apart.
• Examine the new broken or cut edges of the Ulexite, plastic fiber and image guide .
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The end of the plastic fiber is rough and jagged as compared to a nearly clean break on the image
conduit. The Ulexite breaks off along the filed edge.
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Glass and plastic are both "amorphous" materials — which means they lack crystalline form.
Materials like these do not break along straight edges like jewels. The glass image guide produced a
very clean flat break over most of its surface, the way a crystal might break, except near the end. It
breaks like a crystal because glass has a very simple molecular structure that behaves nearly like that of
a crystal once a weak point has been made. Plastic, on the other hand, is composed of very long and
complex molecular chains. Their random and long molecular structure produces very rough breaks.
The Ulexite breaks along its fibrous crystal edges. The broken surface may not be perfectly
smooth, but you will see that the break is always along the long fibrous or crystalline links. The Ulexite
mineral will not readily break in any other direction.
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