Total internal reflection

• optical fibers consist of three main parts: high index core, low index cladding, and buffer layer.
• Cladding is a material with slightly lower refractive index than the optical fiber. This uses the principle of critical angle to allow only those rays on a direct path to travel along the fibre.
• Modal dispersion is the dispersion of the light from the source as it passes through the medium and leads to a narrow pulse becoming broader.
• Material dispersion lead to a shorter wavelength of light to travel faster than a longer wavelength.
• A coherent bundle is where a bundle of optical fibers have the same spatial co-ordinates at each end of the bundle. often used in the transmission of images.
• non coherent bundles are cheaper to produce and do not have the same alignment of spatial co-ordinates. they only transmit light for illumination purposes.
• if angle of incidence is larger than critical angle then total internal reflection occurs.
• light in optical fibers take multiple paths that will take different times , leading to the smearing of the original signal. or pulse broadening.