Phil Boyar
Mr. Wirth
Physics
Fiber Optics
Mr. Wirth
Physics
Fiber Optics
The basis behind fiber optics links back to the physics of it all starting with the idea of total internal reflection. As light travels from an area such as air or water into another area or medium such as Lucite, diamond, back to air or water the light reflects and refracts. Each medium or area has a different or in some cases similar index of refraction. This index of refraction is represented by a number such as 1 for air, 1.33 for water, etc. When light crosses or reaches this barrier between mediums the light is both reflected and refracted at certain angles. In every case however, the light reflects at the same angle that it “came in,” to the cross between the mediums. You measure that angle from the normal. The angle of refraction however, can be measured by taking the sine of the angle of incidence and multiplying it by the index of refraction that the source came from and then dividing it by the index of refraction that it is entering. The final step would be to take the inverse sine of that decimal to find the angle of refraction. However, at the critical angle the refracted light will not go into the second medium and will travel along the surface between the media and the refracted beam will be reflected entirely back into the original medium. This is called total internal reflection. This phenomenon occurs when you take the sine of the angle of incidence multiply it by the index of refraction of the original medium and divide by the index of refraction of the second medium and the number you get is great or equal to one and the inverse sine of that number does not exist. This means that the light will not refract into the second medium but will only reflect back into the original medium. This phenomenon explains how fiber optics work from a physics and total internal reflection perspective.
Actual fiber optics are optical fibers that are long thing strands of pure glass, which can be put on a scale to equal approximately the size of a human hair. These individual strands can be bundled and arranged together into groups called optical cables which are used to send out light signals over longer distances. The actual optical fiber however, is composed of three main parts which combine to create its intricate design. The first part of the fiber is the cladding which is an outer material that surrounds the core and actually reflects the light back in to the core. The core, however, is the thin glass center in which the light travels. The last part is the buffer coating which is a plastic coating that protects the fiber from damage like moisture. Optical cables can contain hundreds or even thousands of these individual fibers and are safely protected from even more damage by the jacket. There are three different types of fibers. There are single-mode fibers, multi-mode fibers and optical fibers made from plastic. The single-mode fibers have a small core and send infrared laser light while the multi-mode fibers have large cores and send infrared light. However, the plastic made optical fibers have large cores and send visible red light like how LED screens work.
The actual cables function because the light in the cable travels through the core by continuously bouncing off the cladding, similar to how light bounces off mirrors, except in this case the cladding provides several mirrors so that the light can keep moving. The cladding is able to do this because it fails to absorb any light and can travel far distances which is a good thing. The light signal also can unfortunately degrade in the fiber because of either impure glass or the wavelength of the light.
There are now due to a great increase in technology, several uses for optical fibers. These uses range from telecommunication systems, medical uses, or anything that requires transmitting light to and from hard to reach places like a dentist’s drill. In addition in the medical field optical fibers are used to transmit images to view the inside of a body. In terms of the telecommunication application the fibers can be used underground or sea to transmit signals over long distances with a low amount of loss of signal. Another great thing about optical fibers are they are very cheap to build and use. They are used in telephones, internet, and pay television systems. Currently there are cables underwater that carry telephone and internet signals across the Atlantic and Pacific oceans. They are also used in those toys that light up at parties that appear to have lighted tips. Technology in this area can only grow to further possibilities because of how cheap and easy it is to use them, and because of its diverse abilities and functions. Fiber optics and the physics of total internal reflection are a great discovery that has benefited our society greatly and we would be unfortunate to not have the privilege of that technology. They are something that most people take for granted and do not think about and should be appreciated for how useful they are and how great they make the world today.
Works Cited
Craig Freudenrich, Ph.D.. "How Fiber Optics Work". March 06, 2001
http://electronics.howstuffworks.com/fiber-optic.htm (March 02, 2008)
Emily , McPherson . "Homework Help: Science: Physics: Fiber Optics." Jiskha:Homework help 1998 March 2,
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