The optical fiber connectors (commonly we call patch cord ) is a length of optical cable with connectors fixed on two ends to realize the optical patch active connection. Pigtail is a length fiber cable with only one connector fixed on one end. If both sides of the connector or its end- face are different, we call it hybrid patch cord. According to the transmission medium, it divides single mode and multimode; according to the connector structure type, it divides FC, SC<, ST, MU,D4, E2000, and LC etc.; according to the polished ceramic end-face, it divides PC, UPC and APC.