The core of optical fibers can be plastic (used for very short distances), but most are made from glass. And glass optical cables are made from silica, which, in pure form, has a very low loss in infrared region of the optical spectrum. Designed for longer distance, very high-performance data networking and telecommunications, fiber optic cable uses light to transmit information while the copper wire uses electricity.
A fiber optic cable is composed of the core, cladding, coating, strengthening fibers and cable jacket, with its core and cladding being the two main elements. The core is the light transmission area of the fiber. The cladding is the layer completely surrounding the core. Surrounding the cladding is usually another layer, called a coating.
The principle of light transmission in an optical fiber is known as the total internal reflection, which states that when the angle of incidence exceeds a critical value, light cannot get out of the glass; instead, the light bounces back in. Based on this principle, light can move easily down the fiber-optic line. When this principle is applied to the construction of the fiber-optic strand, it is possible to transmit information down fiber optic cable in the form of light pulses. The core must be a very clear and pure material for the light or in most cases near infrared light (850nm, 1300nm and 1500nm). That’s why glass and plastic are the main materials for optical fibers.