Fiber optic working principle

Optical fiber is composed of two layers of glass with different refractive indices. Generally, the refractive index of the inner core glass is 1% larger than that of the outer glass. According to the principle of refraction and total reflection of light, when the angle between the inner core and the outer layer is larger than the critical angle for total reflection, the light does not pass through the interface and is all reflected. At this time, the light at the interface through numerous total reflection, in a sawtooth route in the core forward, and finally to the other end of the fiber. Optical fiber has two main characteristics: loss and dispersion. The loss or attenuation per unit length of the fiber is related to the length of the transmission distance of the fiber optic communication system and the choice of the distance between relay stations. The dispersion of an optical fiber responds to delay distortion or pulse spreading, which is very important for digital signal transmission. The pulse spreading per unit length affects the transmission distance and information transmission capacity.