Abstract
Optical Fibres are narrow, long strands of very pure glass, through which we transmit signals as light.
Within an optical fibre there are two different types of glass called the core and the cladding. The core is there to propagate the light along the middle of the fibre and total internal reflection occurs at the boundary between the core and the cladding. The light that is not internally reflected ends up leaving the core and is absorbed by the outer jacket of the fibres. The direction of the light coming into the fibre determines whether the light is reflected or not, in fact this distribution is reflected on the light that comes out as is defined as a Gaussian Beam, and the specific shape of it is defined as the optical mode, and there are multiple based on the gradient or step of refractive index change.