Question

Describe construction and working of an optical fiber. What are the advantages of optical fiber communication over electronic communication?

Answer 1

Hint: Total internal reflection is a phenomenon that takes place when light from denser medium travels to a rarer medium at an angle of incidence greater than critical angle. As the rays bends away from normal in going from denser medium to rarer medium an angle of incidence comes when refracted ray goes along the surface and this angle is called critical angle.

Complete answer:
The principle of optical fiber is based on total internal refraction of light. When a light wave enters the fiber it suffers continuous internal reflections along the length of fiber and then emerges from the other end.

An optical fiber generally have three coaxial regions:
Core: The innermost cylindrical part of fiber which carries the light inside it is the core. The diameter of the core varies as \[8.5\mu m - 63.5\mu m\].
Cladding: Covering of core is known as cladding when light enters the core-cladding interference at an angle greater than critical angle the light gets total internal reflection into the core. Cladding enclose the light within the core. The diameter of the cladding is \[125\mu m\].
Sheath: The outermost covering to protect the structure from the external environment. It is also known as protective buffer coating. The diameter of the sheath varies as \[250\mu m - 900\mu m\].

Working of optical fiber: The light wave entering in the core regions undergoes total internal reflection successively, the angle of incidence and reflection is same. Due to the symmetry of fiber and successive total internal reflections the light wave travels forward along the optical fiber and exits out from the other end of fiber. The reflection inside the core prevents the loss of light energy. And the wave can be guided through a very long distance with minimum losses.

Advantages of optical fiber communication over electronic communication:
Long distance: Fiber communication can be transmitted over long distance effectively and economically as compared to copper wire communication which needs additional equipment for long distance transmission and is also very expensive when compared to the same length cost of optical fibers.
Speed: Optical fiber even in small diameter can have a speed of ten- gigabits per strand whereas copper cannot have this much speed even after aggregation of large diameter of copper wire.

Note:The light waves that occur at the core-cladding interference with an angle more than the critical angle are only subjected to the total interference phenomenon. The waves other than these are lost due to refraction into cladding. Installation of optical fiber and maintenance is very expensive even after so many advantages of optical fiber.Specialized and skilled persons are needed for its installation.