What is Fiber Optics ?

Fiber Optics

     Fiber optics was first thought up in the 1930's, but was not useful until the 1970's. They are constantly being improved all the time. The technology to improve fiber optics includes making the glass fibers better so they are capable of handling more light signals over longer distances.
     Fiber optics is a long glass-like rod that is somewhat bendable. Each rod is about as thick as a human hair. The rod contains special additives inside. When light rays are shined into the rod, the special additives called "cladding" reflect the light back and forth so it zig-zags through the rod instead of leaking out. The light comes out the end of the fiber optic rod with the same quality and intensity as when it was first shined into the rod.
     Fiber optics is a system which transmits signals from one location to another through a thin strand of glass which carries light pulses to carry data. This transmission system works on the same principle that copper wires do, but is done in a different way. Data is encoded from electrical signals into optical light pulses, sent through a glass medium and converted back and decoded at the other end. Both copper and optics use electricity at the end of their lines, but optics uses light in between to carry the data.
     Optical fibers are made up of two types of optically conducting materials. The center is called the CORE, and is the portion which carries the light pulses. It is a glass material which has the higher index of refraction. Around the CORE is a very thin layer of glass called the CLAD. The CLAD has a slightly lower index of refraction and is fused to the CORE which makes a completely reflective interface. A SHEATH layer is wrapped around both to protect them from damage.
     A normal glass fiber is composed of 60% CORE and 40% CLAD, and has a diameter of 0.001 to 0.003 inches. The most common CORE size is 0.0625 mm in diameter and has a CLADDING of 0.125 mm. The smaller the inner CORE the higher the data rate and the lower the attenuation. The attenuation is the optical power loss over a certain distance. A small CORE is used for long distance connections and high data rate transmission applications. The problem with this size though is it requires high-precision connections and light sources. Large CORE fibers are easier to connect, since it is less sensitive to dirt and connector tolerances. Also with larger fibers, more signals can be transmitted.
     Light rays can go through the CORE in two ways, either by a Step-Index or Graded-Index. Step-Index fibers has rays which follow a zig-zag path. Graded-Index fibers have rays which follow a wave path.

A Brief History of Fiber Optic Technology

1840s found optical transmission possible by phenomenon of total internal reflection, which is confinement of light in a material surrounded by other materials with lower refractive index, ie. glass in air
1850s used water flowing from jets to carry light, then found bent quartz rods could carry light and patented them as dental illuminators
1880 Alexander Graham Bell patented optical telephone system
1930s Heinrich Lamm first demonstated images through bundle of optical fibers
1960 glass-clad fibers used versus earlier bare fibers, clad used as the lower refractive index, attenuation is at 1dB/m - good for medical use only, communications needed 20dB/km
1970 under 20dB/km achieved by lowering impurities in silica glass, longer wavelengths, helium-neon lasers, and amplifiers
1977 AT&T and GTE installed first fiber optic communication system, loss of 2dB/km
1999 operate at 1.55 micrometers with loss 0.2dB/km, 5 gigabits per second is common, telephone and cable companies run fiber optic lines to remote sites with other lines from there

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