Special optical fiber has been invented not a long time ago, however it significantly changed the way we transpond signals. It is used in cables and wires to transport information across large distances. It is essentially an extremely thin thread of glass. The cable with such material does not experience energy losses like metal wires do, plus light travels along it with much higher bandwidth. The major improvement of optical fiber is that it’s not affected by any electromagnetic interferences. But since optical fiber operates with different types of signals, they require special equipment for maintenance and repair. Specialized light sources are used to test such optical fiber cables. They emit light with a wavelength we cannot see, and transfer the signal along the cable, measuring the amount of time the signal travels and other parameters required for performing an examination. These light sources can adjust the wavelength of light they emit, so they can be applied with different types of cables and complete various complicated types of tests.