Optical patch cables (pigtails) are used to connect the unterminated strands of the cable to the active network and test equipment, mainly using welding technology. Optical patch cables are segments of optical fiber in a buffer layer with a diameter of 0.9 mm. Equipped with a SC, LC, FC, ST type connector only on one side. Pigtails can be mono or multi-mode. The mono-mode ones were given a yellow color code, while the multi-mode ones were orange.