The fiber-optic cable or, as it is more often called, the optical fiber is a wire consisting of one or several glass or plastic threads. Optical cable is used to transfer a signal inside itself. The principle of operation of an optical fiber cable is based on a physical process known as total internal reflection. Its essence lies in the reflection of electromagnetic waves from the interface of two transparent media, provided that the wave falls from a medium with a large refractive index. Fiber-optic cable is used in many areas, but the most widespread use of it is the construction of fiber-optic communication lines. Optical fiber cable is optimal physical environment for building structured cabling systems. It has many advantages over the use of copper conductors: high bandwidth, high degree of interference immunity, in particular immunity to electromagnetic interference, relatively low weight and volume, low attenuation of the light signal, galvanic isolation of the connected equipment, etc.