Saturday, May 28, 2011

Optical fiber

An optical fiber is a flexible, transparent fiber made of very pure glass (silica) not much bigger than a human hair that acts as a wave guide, or "light pipe", to transmit light between the two ends of the fiber.


Fiber optics, though used extensively in the modern world, is a fairly simple and old technology. Guiding of light by refraction, the principle that makes fiber optics possible, was first demonstrated by Daniel Colladon and Jaqcues Babinet in Paris in the early 1840s

Practical applications, such as close internal illumination during dentistry, appeared early in the twentieth century. Image transmission through tubes was demonstrated independently by the radio experimenter and the Clarence Hansell television pioneer John Logie Baird in the 1920s.

Modern optical fibers, where the glass fiber is coated with a transparent cladding to offer a more suitable refractive index, appeared later in the decade

The emerging field of photonic crystal led to the development in 1991 of photonic-crystal fiber, which guides light by diffraction from a periodic structure, rather than by total internal reflection. The first photonic crystal fibers became commercially available in 2000. Photonic crystal fibers can carry higher power than conventional fibers and their wavelength-dependent properties can be manipulated to improve performance.

Daniel Colladon first described this"light fountain" or "light pipe" in an 1842 article titled On the reflections of a ray of light inside a parabolic liquid stream. This particular illustration comes from a later article by Colladon, in 1884.



Optical fiber can be used as a medium for telecommunication and networking because it is flexible and can be bundled as cables. It is especially advantageous for long-distance communications, because light propagates through the fiber with little attenuation compared to electrical cables. This allows long distances to be spanned with few repeaters.

As sensor

Common uses for fiber optic sensors includes advanced intrusion detection security systems. The light is transmitted along a fiber optic sensor cable placed on a fence, pipeline, or communication cabling, and the returned signal is monitored and analysed for disturbances. This return signal is digitally processed to detect disturbances and trip an alarm if an intrusion has occurred.

Other uses

Fibers are widely used in illumination applications. They are used as ligth guides in medical and other applications where bright light needs to be shone on a target without a clear line-of-sight path

Optical fiber illumination is also used for decorative applications, including signs, art, toys and artificial Christmas trees

A frisbee illuminated by fiber optics

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