Optical Fibers

To encrypt messages using chaotic fluctuations in the intensity of a laser one must first be able to transmit information using lasers.  This is possible using optical fibers, which are hair-thin strands of glass through which pulses of light can be sent over long distances.  A beam of light that enters the fiber on one end is subject to total internal reflection, meaning that no light escapes until it reaches the other end of the fiber.  Thus, an optical signal transmitted on one end can be received in the same form on the other end.  The signal is modulated into varying intensities of light so that when the pulses of light reach the receiver the signal can be converted back into its original form.  Optical communication is favored over earlier forms of communication because the signals travel at the speed of light and are therefore faster than the signals sent using earlier technologies. 

The video below shows footage of Charles Kao, one of the pioneering researchers in optical fiber communications, in his laboratory in 1966.  If nothing else, the video demonstrates how thin the optical fibers are.  The video also mentions that many people were skeptical that such technology could become useful because at that time light was prone to escape the fibers and data was often lost in transmission.  These problems were corrected and fiber optics have became a fundamental part of the world’s communication network.  In fact, Kao was awarded the Nobel Prize in physics last year for his work on fiber optics.

Though this does not deal directly with chaos or encryption, it does help to illustrate the type of communication to which the chaotic encryption techniques described in the readings would be applied.

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