Question

(a) What is the structure of an optical fiber?
(b) What is the principle used for transmitting audio and video signals using optical fiber? Explain the principle.

Answer 1

We know that optical fibers are mostly used as a method of transmitting light between the two ends of the fiber and have wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths than wire cables. Fibers are used in place of metal wires because signals travel along them with lesser amounts of loss; in addition, fibers are also immune to electromagnetic interference, a problem from which metal wires suffer excessively.

Complete step by step answer:
(a) First, we will see the structure of an optical fiber. The basic functional structure of an optical fiber consists of an outer protective cladding and an inner core through which light pulses travel. The diameter of the fiber is about $125\mu m$ and that of the core is just about $50\mu m$.

(b) Now, we will understand the principle used for transmitting audio and video signals using optical fiber which is the principle of total internal reflection. The difference in refractive index (${n_1}$and ${n_2}$) of the cladding and the core allows total internal reflection in the same way as happens at an air-water surface. If light is incident on a cable end with an angle of incidence more than the critical angle then the light will remain trapped inside the glass strand. In this way, light travels very quickly down the length of the cable over a very long distance.

Note: Here, we have seen the construction and principle of optical fiber. An optical fiber can be mainly used for the transmission of light to remote locations. Also, bundles of several thousand very thin fibers assembled precisely side by side and optically polished at their ends, can be used to transmit images.