Explain the principle,construction,and working of an optical fibre.

(N/A) Principle: Optical fibres are based on the phenomenon of total internal reflection.
Construction: Optical fibres are fabricated with high-quality composite glass or quartz fibres. Each fibre consists of a central core surrounded by a cladding. The refractive index of the material of the core is higher than that of the cladding.
Working: When a signal in the form of light is directed at one end of the fibre at a suitable angle,it undergoes repeated total internal reflections along the length of the fibre and finally emerges at the other end.
Since light undergoes total internal reflection at each stage,there is no appreciable loss in the intensity of the light signal. Optical fibres are designed such that light reflected at one side of the inner surface strikes the other at an angle larger than the critical angle. Even if the fibre is bent,light can easily travel along its length. Thus,an optical fibre acts as an optical pipe.
Applications: $A$ bundle of optical fibres can be used for several purposes. $A$ device that converts one form of energy into another is called a transducer. Optical fibres are extensively used for transmitting and receiving electrical signals,which are converted to light by suitable transducers. They are also used as a 'light pipe' to facilitate visual examination of internal organs like the esophagus,stomach,and intestines. Additionally,they are used in decorative lamps where light travels from the bottom of each fibre and appears at the tip as a dot of light.