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Fiber Optics

How fiber optic cables work and what they are used for.

Grace Shears

on 26 April 2014

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Transcript of Fiber Optics

welcome to the world of...
Fiber Optics
what's a "fiber optic"?
The literal definition of "fiber optics" is the use of light through fibers used to transfer information.
The use of fiber optic cables ranges from high speed internet to medical endoscopes. However, to understand these things, one must understand how a fiber optic cable works.
use this
Fiber optic cables are made up of these parts:
Fiber optic cables work by a process called total internal reflection.
Light travels through the core and bounces off its sides, making it unable to shine through the cladding. This leaves the light only able to come out the end of the fiber, as you can see.
This process of total internal reflection only occurs is light enters what is called the “cone of acceptance”.

When light shines through the cone of acceptance, it is shining through the cable at precise angles, so that the light may travel through the cable without escaping. The light waves that are not captured in the cone of acceptance are absorbed by the cladding.
Snell's Law of Refraction
While the core of a fiber optic cable is usually made of small tubes of pure glass, other things can also be used similarly, such as water. As in this video:
Pretty Cool.
So…how does this all MEAN anything?
Well, fiber optic cables actually have many extraordinary uses.
Endoscopes are long, thin fiber-optic cables used in medical and veterinary hospitals. They’re pretty useful because they’re so thin and easy to maneuver. Doctors and veterinarians use them as both a light source and to produce images on a computer screen so they can see inside people or animals.
Telephone Lines
High-Speed internet, Telephone Lines, and Television
Light and optical fibers are used by internet, telephone, and TV companies to transmit signals. Optical fiber is much more effective than the commonly used copper wire over long distances.
The problem with copper wire is that there tends to be a lot of interference and loss of potency of the signals (attenuation). Attenuation affects the propagation of the waves, disturbing the signals to TVs, internet, and phone lines. Copper wire is slowly being replaced with optical fiber. The thing is, fiber optics can really only reach their full potential when used for long-distance communication. So if we used it for short distances, the cost would be higher.
Fortunately, fiber optics are actually becoming more affordable, especially when compared to the price of copper. copper is about $2.68 per foot, while basic fiber optic cables are about $0.55 per foot and heavy duty fiber optic cable is about $1.64 per foot.
All this can be explained by Snell's Law. When looking at a fiber optic cable, an imaginary line called the normal line is drawn perpendicular to the core. When light passes through a medium with one index of refraction (m1) to a medium with a different index of refraction (m2), it refracts away from the normal line. [An index of refraction is the ratio of the speed of light in a vacuum to the speed of light in the medium under consideration).
When the light enters the cone at a certain angle, called the critical angle, the light won’t go into m2. Instead, it will bounce off the surface between the two media (sine [critical angle] = n2/n1 where n1 and n2 are the indices of refraction [n1 is greater than n2] and 01 and 02 are the angles of incidence). If the light waves through m1 are greater than the critical angle, then the refracted beam will be reflected entirely back into m1. This is known as total internal reflection, and it’s how fiber optics work!
Lights are the simplest use for fiber optics. As you saw in the video, light travels through the core of a fiber optic cable and reflects off the walls, coming out the end of the core as light. Fiber optic lights can be decorative (like the one I’ve brought here) and useful. For instance, many traffic lights are fiber optic, as well as lights that illuminate landscapes, swimming pool perimeters, and building outlines.
So...now you can see that fiber optics are not just a cool decoration. They have real world applications!
the end
Full transcript