| If you are forced into a very narrow space, you'll find that any movement of your legs and arms is impossible. Now imagine that your leg and arm movements are a wavelength. Light waves, too, find it impossible to move if they are confronted with a small space. This is our departure point for thinking about near-field light. Let's first consider light traveling along an optical fiber. Light waves can travel freely along optical fibers that are even much thinner than human hair. This is because the diameter of the optical fiber is bigger than their wavelength. What happens, then, if the diameter of the fiber is smaller than that wavelength? The light waves find it impossible to assume their proper form because of the lack of space. They are unable to move as they should, and so make no progress along the fiber. In fact, if you go on reducing the width of optical fibers, you eventually arrive at a point at which light does not penetrate.
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