THE FUTURE OF FIBER OPTICS
Light injected into a fiber can adopt any of several zigzag paths, or modes. When a large number of modes are present they may overlap, for each mode has a different
velocity along the fiber. Mode numbers decrease with decreasing fiber diameter and with a decreasing difference in refractive index between the fiber core and the surrounding area. Individual fiber production is quite practical, and today most high-capacity systems use single fibers. The present pace of technological advance
remains impressive, with the fiber capacity of new systems doubling every 18 to 24 months. The newest systems operate at more than two billion bits per second per fiber pair. During the 1990s optical fiber technology is expected to extend to include both residential telephone and cable television service.
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