What is Fiber Optics?

Structure and Principle

An optical fiber used in light guides consists of a core surrounded by a clad layer (see Figure 1). 
- Core is made of optical glass which has an excellent transmission property. 
- Clad is made of weather-resistant glass, and works as a covering material. 
This structure of fiber allows light to travel along the fiber through repeated total internal reflections* inside the core from one end to the other.

Total internal reflections is the phenomenon that reflection of the total amount of incident light at the boundary between two media (see Figure 2). The phenomenon occurs at the boundary between two mediums having different refractive indices, such that if the incident angle in the first medium is greater than the critical angle, then all the light is reflected back to that medium.