Question

Computer Networks IT 210

Please Use your own words .
sorry No handwriting
no copy paste
Optical fibers use reflection to guide light through a channel. Explain, in your own words, how optical fibers are made in order for the light to be reflected off the cladding instead of refracted into it?
thank you for time

Answer 1

Answer) The main characteristic of Optical FIbres is that they guide visible light from the source to the destination. These are made in such a way that total internal reflection can be achieved in the fibers such that the light remains in the core always. Hence, the fibers can act as a waveguide to the light wave passing in its core. The critical angle holds utmost significance here. Basically, Critical Angle can be defined as the angle which when made by the light wave to the material, the light wave will travel between the 2 medium. This can be seen from the figure given below.

When the angle at which the light wave hits the surface of cladding (m2) is less than the critical angle (Q), the light wave will be normally refracted to the cladding of the fiber. This can be seen from the figure given below.

This critical angle can be defined using the mathematical equation given below.

sine[Q] = m2/m1; This can be derived from the discipline of optics in which refraction between 2 mediums is given by sine (A) / sine (B) = m2/m1; where A is an angle in medium A against the normal and B is the angle in medium B against the normal. Now, when the angle of incidence is greater than the critical angle, total internal reflection occurs. This has been depicted in the figure below.

Now, the cladding and core can be made in such a way that Critical angle is equal to Q = sine^-1 (m2/m1). Here, m1 shall always be greater than m2 and the angle of incidence shall always be greater than the critical angle. Hence, Optical fibers are made in a way to follow the above conditions. These can also be divided among single-mode fiber and multi-mode fiber.