14-08-2012, 10:48 AM
Fiber Optics
Optical fibers Module III.ppt (Size: 857 KB / Downloads: 45)
Introduction: Optical fiber
Optical fiber is a long thin strand of transparent dielectric material (glass or plastic) about the diameter of a human hair.
Optical fiber carries electromagnetic waves of visible and infrared frequencies from one end to the other end of the fiber by means of Total Internal Reflection.
Optical fibers are arranged in bundles called optical cables that can transmit large amounts of information at the speed of light.
Optical fiber consists of three sections
Core: It is an inner cylindrical material made up of glass or plastic.
2) Cladding: It is a cylindrical shell of glass or plastic material in which
Core is inserted.
3) Protective Jacket: The Cladding is enclosed in polyurethane jacket and it protects the fiber from surroundings.
NOTE: The refractive index of core is slightly greater than the refractive index of Cladding. The normal standard values are 1.48 and 1.46 respectively.
How Does Optical Fiber Transmit Light?
Principle: Optical fiber works on the principle of Total internal reflection. Once light ray enters into core, it propagates by means of multiple total internal reflection’ s at core-cladding interface.
The light in a fiber-optic cable travels through the core
(hallway) by constantly bouncing from the cladding (mirror
lined walls), a principle called total internal reflection.
Critical Angle
The critical angle is the angle of incidence above which total internal reflection occurs
From Snell’s law of refraction the angles of incidence and refraction are related to each other & to the refractive indices of the mediums as :