Final answer:
The cladding surrounding optical fibers provides a lower refractive index than the core, which is essential for total internal reflection, thus facilitating the transmission of light signals with minimal loss.
Step-by-step explanation:
The part of the fiber that provides a lower refractive index than the core to ensure total internal reflection is known as the cladding. Optical fibers are carefully designed with a core and cladding that have different refractive indices.
The core, through which the light travels, has a higher refractive index, while the surrounding cladding has a lower refractive index.
This difference in refractive index prevents light from escaping the core, enabling light to be guided along the fiber even around corners and ensuring that most of the light signal is transmitted with minimal loss.
The cladding also adds durability and flexibility to the optical fiber, as it is complemented by an additional protective layer.
Without this cladding, light could pass between fibers in contact with one another, as their indices of refraction would be identical, which would result in signal degradation and the loss of image quality at the receiving end of the fiber.