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| Optical
Fiber Construction |
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Modern optical fibers are formed by two layers of glass. As
shown in fig, the fiber core (8 μ m) is surrounded by a
concentric core of lower index glass known as cladding (125
μ m). |
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The cladding is surrounded by a protective layer. The total
internal reflection occurs as the core-cladding interface. In
fibers designed for high-speed telecommunication, the core is
only a few microns in diameter, not much larger then the wavelength
of the light used. In such cases, the full electromagnetic wave
picture must be describe the propagation of the light. However,
when the highest data transmission rate are not required, fibers
with a "large" core of perhaps a hundred micron or
more used such fibers are known as multimode fibers. For multimode
fibers, ray, picture is adequate to describe the behavior of
the light. |
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