FC/APC single mode fiber optic pigtail combining threaded screw-type coupling with 8-degree angled polish for maximum return loss of 60dB or greater. Green connector body for APC identification. Understanding fiber connector types—SC/APC, SC/PC, LC/UPC, LC/APC, ST/PC, FC/PC, and FC/APC—is essential for selecting the right interface for your application. Each type varies by shape, polish (APC, PC, or UPC), and return loss performance, which affect PC, UPC, and APC Polish Styles: What's the. The LC, SC, and FC indicate the different structures of fiber connector types, whereas the UPC and APC indicate different polishing shapes of fiber connector end faces. FC connectors are used in datacom, telecommunications, measurement. Executive Summary: A fiber optic pigtail is one of the most commonly specified yet least understood components in structured cabling.