In an optical fiber, how does the refractive index of the core compare to that of the cladding?

In an optical fiber, the core needs to have a higher refractive index than the cladding to facilitate total internal reflection. This principle is crucial for guiding light signals along the fiber. When light travels from a medium of a higher refractive index (the core) to one with a lower refractive index (the cladding), it reflects back into the core when it hits the core-cladding boundary at an angle greater than the critical angle.

If the refractive index of the core were lower than or the same as that of the cladding, light would not be effectively contained within the core and would escape into the cladding, resulting in signal loss. Therefore, having a higher refractive index in the core creates an effective waveguide, ensuring that the light signals remain within the fiber and travel efficiently from one end to the other. This characteristic is essential for the function of optical fibers in telecommunications and data transmission systems.