Things About APC Fiber Connectors

The most common SM fiber connector color we encounter is blue type during installation work.  When Comes to a passive optical network (PON), operator network or very large-scale data center, the green color APC fiber connectors are used more common.

It is very important to understand the difference between the two fiber connector with different color to avoid fiber damage or even equipment port damage. For SM, the blue type UPC connector with round surface ferrule endface while blue color represents APC fiber connector with 8 degrees endface. This tiny angle allows the reflected light to be absorbed by the cladding, which reduces the back reflection in the core and provides excellent return loss performance.

Although for fiber optic links, we usually care about insertion loss, however some applications are more susceptible to reflection (return loss). For example, high-power lasers used in long-distance fiber links are very sensitive to reflections, and severe reflections may even damage them. Fiber applications that operate at higher wavelengths (typically 1500 nanometers and above) are also more susceptible to reflection, including wavelength division multiplexing (WDM) applications that use multiple wavelengths to transmit signals, and use of RF signals at higher wavelengths Applications for sending video include PON/GPON deployment.

These applications explain why APC fiber connectors are found to be deployed in service provider networks. As more and more companies and CATV provider deploy PON for their broadband network, more data centers are connected to operator networks and longer single-mode fiber links are deployed With WDM applications, the more APC fiber connectors  application in various environments.

However, It is important to note that the UPC and APC fiber connectors cannot be patched. Not only will the cores not be aligned, but also resulting in severe performance degradation, even trying can cause damage the end faces.

When using APC connection to test a single-mode fiber system, a few things should be noticed. When performing a level 1 insertion loss test, Fluke Networks’ CertiFiber Pro only supports APC fiber connectors at the input ports—the output ports use UPC connectors. Although no damage will occur, a warning will be received from the tester that the received power is too low. The input port uses non-contact patching, so it can accept any type of connector. Therefore, when testing an APC system, two UPC-APC hybrid cables and two APC-APC cables are to be used.