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!

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