UPC or APC – Which One to Choose?

When it comes to fiber optic cables, you might be curious about the description that contains UPC or APC. For example, what is LC UPC to LC UPC? And what is SC APC to SC APC? UPC and APC are actually two polish types of fiber ferrules. This article will help you explore the world of UPC and APC to know which one is the better solution for your network.

What is APC & UPC?

Return loss is inevitable when installing a connector on the end of fiber. It is a back reflection generated by the light source. However, severe light loss will damage the laser light sources and disrupt transmitted signals. Therefore, different polish connector ferrules are made to avoid serious return loss. UPC and APC are two widely used polish types. Here are some specific information about UPC and APC.

UPC, namely ultra physical contact, is evolved from PC with a better surface finish. UPC connector relies on machine polishing to deliver its low optical return loss characteristics. Its rounded finish created during the polishing process allows fibers to touch on a high point near the fiber core where light travels. In addition, when using the UPC connector, make sure your laser’s specifications can handle the return loss your UPC connector will generate.


APC, namely angled physical contact, is very different from UPC. The end face of APC connector is precisely polished at an 8-degree angle to the fiber cladding so that most return loss is reflected into the cladding where it cannot interfere with the transmitted signal or damage the laser source. But it is extremely difficult to field terminate an APC connector at 8 degrees with any consistent level of success. Therefore, if an APC connector is damaged in the field, it should be replaced with a factory terminated APC connector.


How to Distinguish UPC from APC?

Many differences can be found between UPC and APC connectors:

Point one, end faces. As we have discussed before, UPC connectors are polished with no angle, but APC connectors is polished at an 8-degree angle.

Point two, ways of light reflection. Their different polish end faces directly lead to their differences in ways of light reflection. Any reflected light is reflected straight back towards the light source if an UPC connector is used. But the APC connector causes reflected light to reflect at an angle into the cladding instead of straight back toward the source.

Point three, return loss. Since their light reflection patterns are varied, their levels of return loss are also different. APC connector offers lower return loss of -65 dB than UPC of -50 dB. As a matter of fact, connectors can achieve better matching performance if return loss is lower.

Point four, connector color. This is the most obvious difference that can be seen from the surface. UPC connector usually has a blue body while APC connector has a green body.

Which One to Choose?

If you are still confused about which polish type to choose, the best way is to see whether their applications complies to yours. In general, the APC type has a better performance than the UPC type. APC is best for high bandwidth applications and long haul links. For example, FTTx (fiber to the x), passive optical network (PON) and wavelength-division multiplexing (WDM) that are more sensitive to return loss, thus APC is a better solution to offer the lowest return loss. However, massive employment of APC connectors will cause higher cost. In this way, UPC might be a better choice because cost budget is of equal importance.


UPC and APC are taken into consideration when choosing fiber optic patch cables. Both of them can reduce light loss and protect laser sources from damage. A wise selection should be based on your actual condition. Hope this article can provide you some help.

Introduction of PC, UPC and APC Connector

When we choosing a LC connectors, you might hear descriptions like LC UPC polished fiber optic connector, or LC APC fiber optic connector. Or when you are choosing a ST fiber optic patch cable, you can find the description like ST/PC multimode fiber optic patch cable. What do PC, UPC, APC stand for? The following text will give the explanations.

fiber optic connector ferrule

PC (physical contact), UPC (ultra physical contact) and APC (angle physical contact) are the polish style of ferrules inside the fiber optic connectors. Unlike copper cables with copper wire in the connectors as connection media, fiber optic connectors are with ceramic ferrules for connection. The picture on the left shows the ferrule in fiber optic connector. Different fiber optic connectors has different ferrule size and length. Also their polish style might be different.

To better understand the why we have PC, UPC and APC, let’s start with the original fiber optic connector which has a flat-surface and is also known as flat connector (showed in the following picture). When two flat fiber connectors are mated, an air gap naturally forms between the two surfaces from small imperfections in the flat surfaces. The back reflection in flat connectors is about -14 dB or roughly 4%. To solve this problem, the PC connectors came into being.

flat fiber connector

In the PC connector, the two fibers meet, as they do with the flat connector, but the end faces are polished to be slightly curved or spherical. This eliminates the air gap and forces the fibers into contact. The back reflection is about -40 dB. The following picture shows two end faces of PC connectors.

PC connector

UPC connector, usually has a blue-colored body, is an improvement to the PC connector with a better surface finish (as showed in the following picture) by an extended polishing. The back reflection of UPC connector is about -55 dB which lower than that of a standard PC connector. UPC connectors are often used in digital, CATV and telephony systems.UPC connector

PC and UPC connectors have reliable, low insertion losses. However, their back reflection depends on the surface finish of the fiber. The better the fiber gain structure, the lower the back reflection. If the PC and UPC connectors are continually mated and remated, back reflection will degrade. An APC connector won’t have such problem. Its back reflection does not degrade with repeated matings.

APC connector

APC connector usually has a green body with an end-face still curved but are angled at an industry-standard 8 degrees (showed in the above picture) which allows for even tight connections and smaller end-face radii. Thus any light that is redirected back towards the source is actually reflected out into the fiber cladding, again by virtue of the 8 degree angled end-face. APC ferrules offer return losses of -65dB. Some applications that are more sensitive to return loss than others that call for APC connectors, like FTTx and Radio Frequency (RF) applications. APC connectors are also commonly used in passive optical applications due to the fact that many of these systems also use RF signals to deliver video.

APC connector and UPC connector

PC, UPC or APC, which should be the choice of fiber optic connector? The answer is it depends. Choosing the appropriate connector for a fiber network depends on things such as, network design and function. Fiberstore offers a wide range of fiber optic connector as well as professional optical network solution. For more information you can visit Fiberstore.