Fiber Optic Cable ‒ Detail

When a wave reaches a boundary between two different materials with different refractive indices (different speed of the wave in each medium), the wave is partially refracted at the boundary surface, and partially reflected. Since the speed is higher in the second medium, the angle of refraction is greater than the angle of incidence. The angle of incidence at which light is refracted such that it travels along the boundary is called the critical angle. If the angle of incidence is greater than the critical angle, then the wave will not cross the boundary, but will instead be totally reflected back internally. An optical fiber works on the principle of total internal reflection. An optical signal inside the fiber is the product of a modulator, which transform electric signals to optic signals. The signal travels through the fiber, but it is amplified periodically by repeaters. At the final destination, the detector receives the signal, converting it back to an electrical signal. Digital signals are a series of pulses with two states (1,0). Light can be used for digital communications, such as in Morse code. Optical fibers can carry information coded in light waves or infrared waves.