Introduction
Before discussing PC, UPC and APC fibre connectors, it should be known that the two end faces of the fibre must be precisely connected in order to maximise coupling of the fibre light output from the transmitting fibre to the receiving fibre. The accuracy of connection depends primarily on the quality of the physical connection of the fibre, both of which relates to the insertion loss and return loss of the fibre. The performance of the optical fibre is precisely measured by the insertion loss and return loss. The physical connection of the fibre, sometimes referred to as the different polished fibre end face shapes, is therefore critical to the performance of the fibre. According to the type of polishing of the connector, fibre optic patch cords are divided into PC, UPC and APC types. The three polishing methods of fibre optic patch cords are different in structure and performance, mainly in terms of insertion loss and return loss. Of these, APC is by far the most popular type of polishing.
What is a PC Connector?
The term "PC connector" refers to a physical contact fibre connector, which enables two fibres' end faces to make direct touch with one another. PC connector uses microspherical polished connectors with a black colour. The fibre-end surface has been polished to resemble a convex sphere. Despite the huge radius of curvature, it appears flat. Because the optical fibre core is situated at the maximum point of bend, the air gap between fibre components is effectively reduced, allowing physical contact between two fibre end faces.
The fibre optic PC connector is the oldest one among the three connectors. The nearly flat end face construction is insufficient to cut down on return loss. The PC connector was abandoned in favor of enhanced UPC and APC connectors because it had a reasonably large return loss of at least -40dB.
What is a UPC Connector?
UPC connector is an improved and upgraded version of PC. "UPC" is the abbreviation of Ultra Physical Contact. The UPC fibre connector is an evolution of the outdated PC connector with a blue colour. 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 two fibre-end surfaces to engage each other more precisely. Additionally, it makes use of an improved publishing method, which improves the fibre surface polish. Therefore, the UPC polish connector has a lower return loss of -50dB than the PC connector. As a result, the UPC polish connector, in comparison to the PC connector, has a lower return loss of -50dB.
What is an APC Connector?
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.
How to Choose Between UPC and APC?
APC connector is more recommended if your application, such as FTTx and WDM system applications, is sensitive to return loss. Given that UPC connectors is less expensive than APC connector, it can be the ideal option for less sensitive applications because it can provide performance that is almost identical to APC. Therefore, it is clear that UPC connector is frequently utilized in fibre networks today.