Pigtail, also known as pigtail, has only one end with a connector, and the other end is a broken end of a fiber optic cable core. It often appears in fiber optic terminal boxes. (couplers, jumpers, etc. The connector end is polished and tested under factory conditions, ensuring low insertion loss and high return loss. One. A fiber optic pigtail is a short, usually unjacketed, optical fiber cable that has a factory-installed connector on one end and a length of exposed fiber at the other.