When light passes through an optical fiber, it undergoes a phenomenon called total internal reflection, which causes the light to propagate in a curved path within the fiber. Total internal reflection occurs at the boundary between two mediums when the light is incident at an angle greater than the critical angle.
An optical fiber consists of a core, which is the region where light travels, and a cladding, which surrounds the core and has a lower refractive index. The refractive index is a measure of how much a medium slows down light compared to a vacuum. The core and cladding are carefully designed to have different refractive indices.
When light enters the core of an optical fiber, it encounters the core-cladding boundary. If the incident angle is smaller than the critical angle, the light passes through the boundary and continues propagating straight through the fiber. However, if the incident angle is larger than the critical angle, total internal reflection occurs.
Total internal reflection causes the light to bounce back into the core instead of crossing the core-cladding boundary. This bouncing back of light keeps the light within the core and guides it along the fiber. Each time the light encounters the core-cladding boundary, it undergoes total internal reflection, resulting in a zigzag path within the fiber.
The curved path of light within the optical fiber allows it to travel long distances with minimal loss. As long as the incident angle at the core-cladding boundary is larger than the critical angle, the light will continue to undergo total internal reflection and follow the curved path, effectively propagating through the fiber.
The phenomenon of total internal reflection is crucial for the functioning of optical fibers, which are widely used in telecommunications, data transmission, and other applications where efficient and low-loss transmission of light is desired.