When you build or upgrade a fiber network, the same four words pop up everywhere— fiber optic (bare fiber), pigtail, patch cord, optical cable. They're related, but they are not interchangeable. Mixing them up drives costs higher, increases loss, and slows your rollout. The. Executive Summary: A fiber optic pigtail is one of the most commonly specified yet least understood components in structured cabling. The good news? Once you nail. A fiber pigtail is a single, short, usually tight-buffered, optical fiber that has an optical connector pre-installed on one end and a length of exposed fiber at the other end.