According to the return loss, ceramic ferrule end faces of fibers are classified into PC, UPC, and APC, as shown in Figure 8-20. Our high precision standard zirconia ferrules are designed for high reliability and performance. The optical fiber is located in the center of the ferrule, and the two fiber end faces make direct contact during connection to reduce reflections caused by air gaps. PC, APC, and UPC are three different ferrule polishing methods, representing the structural differences of the front face of the ceramic ferrule.