APC vs UPC vs PC Fiber Connector, What is the Difference?
If you look at your fiber cabling systems, you may find essential gear like fiber connectors and fiber optic cables. They may have different end-face polish and color codes. Many people may need to become more familiar with the difference between APC vs UPC vs PC polished fiber connectors. Please read this article and take the time to understand the details of how they differ.
What is Flat Fiber Connector?
The flat fiber connector is like the figure above; the most apparent feature is the FLAT end face. When two flat fiber connections are joined, they naturally create a little air gap between the two ferrules, which is their main problem. This is partially due to the connectors’ relatively broad end faces, which enable numerous minor but noticeable defects to accumulate on the surface. With a core size of only 8 to 9 µm, this is not very useful for single-mode fiber cables, necessitating the development of Physical Contact (PC) connectors.
What is PC Fiber Connector?
PC is an abbreviation for “physical contact”. PC fiber connector refers to the connector with physical contact polished. It was first created in the 1980s to overcome the shortcomings of the original flat fiber connector.
Unlike flat fiber connectors, physical contact connectors have a slight taper around the endpoint. The cylindrical taper created by polishing the fiber ends reduces the air gap between the fiber ends that often occurs with flat connectors. Correspondingly, this small air gap reduces optical return loss (ORL), reducing the amount of light returning to the power supply and improving overall signal quality.
Generally, the typical return loss in single mode applications is about -40 dB, higher than the original flat polished style (-14 dB or about 4%). They are commonly used in multimode and single mode applications. However, as times have changed, this polishing style has become obsolete and is gradually replaced by the UPC polishing style.
What is UPC Fiber Connector?
UPC stands for Ultra Physical Contact. In fact, it is an enhanced version of the PC fiber connector. Based on the convex face properties of the PC, the connector utilizes an extended polishing method to create a better surface finish on the fiber.
Compared to standard PC connectors, this extended polishing results in lower optical return loss (ORL). Because of superior insertion and return loss performance, They have been used in many networks like digital TV, telephone, and data systems.
What is APC Fiber Connector?
APC stands for Angled Physical Contact. The emergence of APC fiber optic connectors is to achieve the need for lower back reflection. By grinding the radius of the end face of the fiber ferrule to an angle of 8°, we can minimize the back reflection. While that may not seem like much, the angled edges change the pitch at which light bounces back. So light reflected from the APC end face is directed into the cladding surrounding the fiber optic cable, rather than returning more directly to the fiber core.
The insertion loss of the APC fiber connector is comparable to that of the UPC fiber connector. Still, it can achieve a better optical return loss (-60dB or lower), which is better than other connectors.
But remember, unlike flat, PC, and UPC fiber connectors, this slight angle on the APC connector creates a rotation problem. Therefore, it can only be mated with other bevel-polished connectors, not with regular PC and UPC connectors paired, which would otherwise cause very high insertion loss.
APC connectors are commonly used in passive optical networks (PON) deployed in RF video or fiber-to-the-home (FTTP) networks because these systems are sensitive to any back reflections from connectors within the network.
APC vs. UPC vs. PC: What Are Their Differences?
Learning from the definition of APC, UPC, and PC fiber connectors, the most obvious difference is the fiber end face, return loss, and overall performance. Let’s look at the critical differences in the following chart.
