How do optical fibres use total internal reflection in communication?

Optical fibres use total internal reflection to transmit light signals over long distances without significant loss.

Optical fibres are thin strands of glass or plastic that are used in telecommunications to transmit information in the form of light signals. The principle of total internal reflection is fundamental to their operation. This is a phenomenon that occurs when a wave, such as light, hits a medium boundary at an angle greater than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary, no light can pass through and all of it is reflected back into the original medium.

In the case of optical fibres, the fibre core, through which the light travels, has a higher refractive index than the surrounding cladding. This means that when light hits the boundary between the core and the cladding, it is reflected back into the core if the angle of incidence is greater than the critical angle. This causes the light to bounce back and forth along the length of the fibre, effectively trapping it within the core. This is total internal reflection.

The light signals can thus be transmitted over long distances with minimal loss of signal strength. This is because the light does not escape from the fibre, and the signal does not weaken as it travels. This makes optical fibres an efficient means of communication, capable of carrying large amounts of data quickly and reliably.

In summary, optical fibres utilise the principle of total internal reflection to guide light signals along their length. The higher refractive index of the fibre core compared to the cladding ensures that the light is reflected back into the core, allowing the signals to be transmitted over long distances without significant loss.