Single Mode Fiber Optic Patchcords are available with FC/PC or FC/APC terminated connectors. Hybrid terminated connectors enable users to adapt FC/PC or FC/APC patchcords for compatibility with existing fiber assemblies. What are the differences between these polish. In fiber optic communication systems, the polishing type of fiber patch cord interfaces directly affects key performance metrics such as insertion loss (signal attenuation during transmission) and return loss (unwanted signal reflection). They act as the critical link for interconnecting devices like optical switches, servers, and distribution frames. To put it simply, PC, UPC, and APC define the type of polish used on the fiber optic connector end face or ferrule.