OPTICAL FIBRES

Optical fibers are the waveguides through which electromagnetic waves of optical
frequency range can be guided through them to travel long distances.

An optical fiber works on the principle of total internal reflection (71R).

When light enters through one end of optical fiber it undergoes successive total internal
reflections and travel along the fiber in a “zig-zag” path.

 Optical fibers are made up of glass, plastic or SiO2 as thin as size of human heir.
 An optical fiber consists of three (3) co-axial regions.

The inner most region is the light-guiding region known as “Core”. It is surrounded by a
middle co-axial regional known as “cladding”. The outer most region which completely
covers the core & cladding regions is called “sheath or buffer jacket”.

Sheath protects the core & cladding regions from external contaminations, in addition to
providing mechanical strength to the fiber.


 The refractive index of core (n1) is always greater than the refractive index of cladding
(n2) i.e., n1 > n2 to observe the light propagation structure of optical fiber.