- An optical fibre cable consists of a core and a cladding, both made of dielectric materials. The core has a higher refractive index than the cladding. - Light signals are transmitted through the core of the fibre. When light enters the core at an angle relative to the axis of the fibre, it strikes the boundary between the core and the cladding. - If the angle of incidence at the core-cladding boundary is greater than the critical angle (determined by the refractive indices of the core and cladding), the light undergoes total internal reflection and is reflected back into the core. - This process repeats as the light travels along the fibre, confining the light within the core and allowing it to propagate over long distances with minimal loss.