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Optical fibers are arguably one of the world's most influential scientific developments from the latter half of the 20th century. Normally we are unaware that we are using them, although many of us do frequently. The majority of telephone calls and internet traffic at some stage in their journey will be transmitted along an optical fiber. Why has the development of fibers been given so much attention by the scientific community when we have alternatives? The main reason is bandwidth – fibers can carry an extremely large amount of information. More indirectly, many of the systems that we either rely on or enjoy in everyday life such as banks, television and newspapers as (to name only a very limited selection) are themselves dependent on communication systems that are dependent on optical fibers.
2. Fundamentals of Fibers
Total Internal Reflection:
From Snell's Law we find that refraction (as shown by the dashed line) can only occur when the angle theta1 is large enough. This implies that as the angle is reduced, there must be a point when the light ray is reflected, where theta1 = theta2.The angle where this happens is known as the critical angle.
CONSTRUCTION OF FIBERS:In fibers, there are two significant sections – the core and the cladding. The core is part where the light rays travel and the cladding is a similar material of slightly lower refractive index to cause total internal reflection. Usually both sections are fabricated from silica (glass). The light within the fiber is then continuously totally internally reflected along the waveguide.
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