Elenco Fiber Optics Voice Data Kit User Manual download pdf (Page 6)

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What exactly is Fiber Optics?

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One dictionary defines fiber optics as:

1. The branch of optics dealing with the transmission of light and images, as around bends

and curves;

2. The fiber thus used.

In our first experiment we will show how a simple plastic rod can guide light from one point to

another in a "fiber optic" manner.

Penlight (you must provide and install 2 AA batteries)

Black rubber penlight boot

3 mm (1/8 inch) diameter plastic rod, 30 cm (12 inches) long

• Dim the room lighting and turn on the penlight. Point it at a wall. Observe the size of the light

beam on the surface as you move the light closer to the wall. Notice the beam size when the

light is approximately 30 cm (12 inches) away.

• Fit the black rubber boot over the bulb end of the penlight, then insert one end of the plastic rod

into the hole in the rubber boot.

• Observe the bright white light which appears at the other end of the acrylic rod.

• With the plastic rod in the boot, point the rod tip toward a wall and observe how the size of the

light spot changes as you vary the distance from rod tip to the wall.

• Look carefully to see if you can observe any light

inside

the plastic rod. (It may be necessary to go

into a dark room.)

• Now grip the plastic rod in the middle by clutching it inside your fist. Is the intensity of the light

coming from the tip now more, or less, than it was before you gripped the rod? Turn the

penlight off.

Light from the penlight bulb should enter one end

of the plastic rod and exit the other end. When the tip of

the rod is close to the wall, the size of the light beam

should be small. When you dim the room light you

should see light a small amount of light inside the rod.

Light entering one end of the acrylic rod is trapped inside until it exits the other end. This

happens because of a material characteristic called optical density. The optical density of the rod is

greater than the optical density of the air around the rod. Because light is confined in the rod, it doesn't

spread until it leaves the tip. Contrary to popular belief, light can't be seen as it passes through the air.

The "light beam" you may see traveling through space from the projector in movie theaters is actually

light being reflected off dust particles in the air. The light you see inside the rod is caused by

imperfections in the plastic which cause light to scatter.

German mathematician and astronomer Johannes Kepler (1571-1630) is known chiefly for his

discovery that the planets move in elliptical (oval-shaped) orbits. However, he also published a book in

1604 called Astonomiae pars Optica. The publication explained, with the help of several experiments,

how light travels in straight lines, casts shadows, and bends when it moves from one substance to

another. He was well ahead of his time.

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Elenco Fiber Optics Voice Data Kit User Manual Page 6

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