Single mode fiber pigtails use 9/125 µm fiber, typically with a yellow jacket. These are ideal for long-distance, high-bandwidth transmission and are widely used in telecom and WAN applications. 5/125 µm or 50/125 µm fiber, with orange or aqua. What is a Fiber Optic Pigtail? Fiber optic pigtail is a cable that only one end is terminated with connectors, which is used to connect to optical devices. The other end can be melted with optical fiber for a permanent connection. 5m to 2m—that has a factory-terminated connector on one end and bare fiber on the other end.