PC UPC APC Fibre Connector Types Comparison

Before discussing PC, UPC, and APC fiber optic connectors, it should be known that the two end faces of the optical fiber must be connected accurately in order to maximize the coupling of the optical fiber light output from the transmission fiber to the receiving fiber. The connection accuracy mainly depends on the physical connection quality of the optical fiber, both of which are related to the insertion loss and return loss of the optical fiber. The performance of the optical fiber is accurately measured by the insertion loss and return loss. Therefore, the physical connection of the optical fiber (sometimes referred to as the different polished fiber end face shapes) is crucial to the performance of the optical fiber. According to the polishing type of the connector, the optical fiber patch cord is divided into PC, UPC, and A PC types. The three polishing methods of the optical fiber patch cord differ in structure and performance, mainly in insertion loss and return. Among these, APC is by far the most popular type of optical polishing.

"PC connector" refers to a physical contact fiber connector, which makes the end faces of two optical fibers directly contact. PC connectors use a black micro-ball polished connector. The fiber end face is polished to make it look like a convex ball. Despite the huge radius of curvature, it looks flat. Since the fiber core is located at the maximum bending point, the air gap between the fiber components is effectively reduced, allowing physical contact between the two fiber end faces.

The fiber PC connector is the oldest of the three types of connectors. The nearly flat end face structure is not enough to reduce the return loss. The PC connector was abandoned in favor of the enhanced UPC and APC connectors because its return loss is quite large, at least -40dB

 The UPC connector is an improved and upgraded version of the PC. "UPC" is the abbreviation of Ultra Physical Contact. The UPC fiber connector is an evolution of the outdated PC connector, and its color is blue. It still has a convex spherical surface, but its radius of curvature is lower than that of the PC connector, giving it a more dome-like appearance. The sharp curve makes it possible for the two fiber end surfaces to contact each other more precisely. In addition, it uses an improved release method that improves the fiber surface polishing. Therefore, the return loss of the UPC polished connector is lower than that of the PC connector, at -50dB. Therefore, compared with the PC connector, the return loss of the UPC polished connector is lower, at -50dB.

APC connector is the most popular fibre connector type in use today . “APC” stands for Angled Physical Connector. With a green colour, the 8-degree bevelled angle of the ferrule end face is particularly beneficial for the secure connection of the fibre end faces. The return loss of the fibre optic APC connector is typically -60dB, which is the smallest among the three types of UPC, APC and PC fibre connectors.

Rather than backward reflecting to the light source, the APC connector considerably lowers fibre return loss by allowing light to reflect to the fibre cladding because of the sloping end faces. It normally has a return loss of -60dB, which is the lowest among the three types of UPC, APC and PC fibre connectors.

  If your application, such as FTTx and WDM system applications, is sensitive to return loss, then APC connectors are more recommended. Since UPC connectors are cheaper than APC connectors, it may be an ideal choice for less sensitive applications as it can provide almost the same performance as APC. Therefore, it is obvious that UPC connectors are frequently used in today's fiber optic networks.