What you need to know PC, UPC and APC connectors

You often read things like FC/PC Simplex Multimode connector, LC/APC Simplex Single mode connector or SC/UPC Simplex Single mode connector, but what do all those words mean? Specifically PC, APC, and UPC.

PC, UPC and APC are acronyms for: 

  • Physical Contact
  • Ultra Physical Contact
  • Angled Physical Contact

PC-UPC-APC

They refer to the way the connector ferrule, the tiny ceramic structure that holds the fiber, is polished. In simple words, they are end-face configurations that are present in numerous connector types.

And as the names suggest, all the polishing styles are different.

The difference between ferrule end-faces results in different performances regarding the connector’s losses, which are:

  • Optical Return Loss: Also called back reflection, refers to the light that is reflected right back into the source that generated it, which damages Laser Light Sources and disrupts signals. This percentage of reflected light is expressed in a negative dB value (the higher the value, the better).

  • Insertion Loss: It is the light loss that happens when a fiber component is inserted into another one to create a fiber optic link. It could be caused by absorption, bending or air gaps between components.

Connectors’ performance characteristic:

PC

PC connectors end faces are polished with a slight curvature. That convex shape locates the fibers at the highest point of the surface, which reduces air gaps between them. Typical return loss in these connectors in single mode applications is -40 dB.  

UPC

An extended polishing is given to these connectors end faces, which results in a better surface finish. The curvature makes them look dome-shaped. Their optical return loss is about -50 dB or higher.  

UPC connectors are generally used in Ethernet network equipment such as serial devices, media converters, and fiber switches. They are also implemented in telephony and data systems.

 

APC

Its ferrule is polished with an 8-degree angle that end-face brings the fibers tighter and reflects light at an angle into the cladding instead of reflecting it directly to the light sources, which causes its Optical Return Loss to be -60dB or higher, being the better performance connector.

APC connectors handle multi-play systems which are why they are mostly employed in Radio Frequency (RF) applications, like CATV or Distribution Antenna Systems.

They are also used in optical passive applications, such as PON networks architectures or passive optical LANs.

The ORL between PC, UPC and APC might not sound as much.

but,

It is since the decibel scale is not linear. So a return loss of -40 dB means 0.01% of the light is reflected back, - 50 dB means 0.001% and -60 or higher means just 0.0001% of light is reflected back into the light source, which is why just APC connectors handle the demands of multi-play services.

Insertion Loss

Typical insertion loss In PC, UPC and APC connectors should be less than 0.3dB. Insertion loss can also be caused by a tiny particle of dust trapped between the connector end-faces. A single dry debris particle could even damage the fibers and ferrules. 

An important thing you have to keep in mind is that APC and UPC connectors can’t be mated together because doing so will cause poor performance or may damage the connectors.

Choosing the right connector

Choosing the right connector for a network depends on the network design and function. UPC connectors are generally used in Ethernet network equipment such as serial devices, media converters, and fiber switches.

They are also implemented in telephony and data systems.

Instead, APC connectors handle multi-play systems which are why they are mostly employed in Radio Frequency (RF) applications, like CATV or Distribution Antenna Systems. They are also used in optical passive applications, such as PON networks architectures or passive optical LANs.

Therefore it is unfair to say that one connector beats the others because it depends on of your particular needs, high application systems should use APC connectors but with fewer quality systems it is okay if you use UPC. 

With the collaboration of Edward J. Forrest. Jr. from Fiber Optic Precision Cleaning.

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