I’ve come across various articles online that explain the differences between APC and UPC, where the former has an angled polish and the latter is a straight “cut”.

Some of them explain that UPC and PC are very similar but that UPC seems to be an evolution of PC with a smaller mating surface.

However, other material I found suggested that UPC has a slight bevel compared to PC.

Now I am wondering, am I able to use the two interchangeably or will I ruin the connectors if I use, say, a female PC connector with a male UPC or vice-versa? Does the answer to that question also apply for transceivers?

2 Answers 2



PC, SPC and UPC are just different polish grades of perpendicular, physical contact connectors. Their end-faces match, so they work nicely together.

In contrast, APC uses an angled surface (usually 8°) that needs to be matched with the same type. Using different APC types or trying to match them with PC/SPC/UPC will cause severe attenuation up to link loss and might even damage the connectors. APC was created to significantly reduce return back reflection as required for passive optical networks (PON) and also beneficial for "bidi" variants using WDD. However, APC has slightly higher insertion loss (attenuation) than UPC (due to both ends being stressed off their contact point).

APC connectors are usually green, and PC/SPC/UPC ones grey (for multi-mode) or blue (for single-mode).

  • Thanks for the extra insight regarding PON and bidi! That was new to me.
    – comfreak
    Jun 13, 2022 at 20:37

the physical and mechanical properties of APC connector are quite different. This means APC should not be mated with UPC or PC. If someone does that, it will destroy the connectors. Plus, it’s not recommended to use APC connectors in fiber SFP modules. Unless the transceiver module has stated clearly that the APC connectors are allowed, users may use UPC connectors. If the network requires a connection between a fiber SFP module and an APC connector, users must use a conversion patch cable (UPC to APC) to connect from a transceiver with flat UPC/PC interface to an angled APC interface.


  • The figure for APC in that link is wrong. What is shown like a flat surface is really similarly rounded like UPC, just tilted out of the axis.
    – Zac67
    Jun 14, 2022 at 15:31
  • Thanks for the input, but my question was less about APC vs (U)PC but instead PC vs UPC.
    – comfreak
    Jun 15, 2022 at 13:06

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