The optical phenomenon that is responsible for the propagation of light signal through an optical fibre is

The propagation of light signals through an optical fiber is primarily governed by the principle of total internal reflection (TIR). An optical fiber consists of a high refractive index core surrounded by a lower refractive index cladding [3]. When light enters the fiber and strikes the core-cladding interface at an angle of incidence greater than the critical angle, it is reflected back into the core rather than being refracted into the cladding [3]. This process allows the light ray to undergo successive reflections, effectively guiding it along the length of the fiber with minimal loss. While phenomena like scattering and dispersion can cause signal attenuation or distortion, they are not the mechanisms responsible for the actual propagation and confinement of the light within the fiber waveguide.

Sources

1. [3] https://www.sciencedirect.com/topics/earth-and-planetary-sciences/optical-fiber