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The
Fiber Optic Principal
The first question we are asked at Fiber Optic Products, Inc. is "What is Fiber Optics, and how does it work?" Well this little page should answer those questions.
Fiber Optic Fibers have
been around for more then forty years, and since then they have become more cost
effective and stronger. Plastic fibers are made with chemicals, the CORE is
Polymethyl Methacrylate polymer (PMMA), and the CLAD is a thin layer of Fluorine
polymer. The Core carries the light down the Fiber while the Clad is the
reflective surface the light bounces off of! The diagram below shows what
happens to light as it enters and travels through the fiber. Light enters
through one end of the fiber and is "Reflected" to the other end, if
the angle of the light is to great the light will not enter the fiber correctly
and refraction will be lost. Skewed fiber is when the ends are not cut parallel
to the 90-degree axis of the fiber. Light is also lost if the ends are not
polished; to polish the ends of fiber you can use a 600 grit wet-dry sandpaper
and finish with a 3m polishing film or a 1500 or greater sandpaper. The fiber
has a 17% Clad which doesn't carry light, so the transmission of a one foot
piece of fiber is in the area of 60-65%.
If light enters one end of a fiber, it will
travel through the fiber with very low loss, even if the fiber is curved. The
principle that makes this transmission of light work depends on the total of
internal reflection. The light traveling inside the fiber center, or core,
strikes the outside surface at an angle greater than the critical angle, so that
all the light is reflected toward the inside of the fiber without loss. This
allows the light to be transmitted over long distances by being reflected inward
thousands of times. To keep the light from loosing its power and to avoid losses
through the scattering of light by impurities on the surface of the fiber, the
optical fiber core is covered or (clad) with a glass (or plastic) layer of a
much lower refractive index; the reflections occur at the interface of the glass
fiber and the cladding."
Remember 'Reflection' means bouncing
off, while 'Refraction'
means bending, although light traveling through a curved optical fiber is not
actually bent; light rays will always travels in a straight line. Confusion
between the term's 'reflection' and 'refraction' occurs in this
case because Snell's law, which is generally taken as the law of refraction,
describes the total reflection that takes place in a fiber. In most cases we do
not pay attention to the fact that in most reflective objects there is some loss
due to transmission (ignoring losses due to scattering) and absorption. The very
best front-surface mirrors used in cameras and other optical devices reflect
only 96 to 98 percent of incident light. Fibers are optimized for the color
(wavelength) of the light that they are intended to transmit. The factors are
indices of refraction for core and cladding (critical angle), impurities or
(dispersion), evenness of core diameter and core surface quality (minimum path)
and bundle fusion techniques (axis parallelism, etc.). Most commercial fibers
are not optimized for white light. But for most hobbyists that is of little
concern because the length of the fiber is typically low and the distance of its
transmission is not a major factor.
We measure the fiber in unit microns, so 1000um
= 1mm. Get it! OK now lets let "Lenny the LED" shows us how his light
travels down the Fiber . . .
Fibers can be used for
many projects from hobbies to communication and come in Glass or Plastic. We
here at Fibers Optic Products carry only Plastic Fibers because of their low
cost and easy bending and cutting abilities. Fiber optic lamps of the 60's &
70's now making a come back, were the most known use of fibers, but now you see
fibers being used on signs, costumes, automobile dash boards, and models. They
come in Bundles, Bristles, Ribbon, Simplex, Duplex, Jacketed & Unjacketed.
One LED can
light-up thousands of fibers so you see the energy effectiveness of how Fibers
can save time and money for all of us! So come on try some FIBER!