Some information about the difference between APC and UPC

You will notice that the connectors, whether they are SC or LC, will be color coded. Green connectors/bulkheads are for APC, while Blue connectors/bulkheads are for UPC. However the main reason for APC, as far as RF overlay is concerned in PON deployments, is for back reflectance control. Once RF is introduced into the PON on the 1550nm wavelength, every bulkhead, split and splice introduces some amount of back reflectance. RF is not very tolerant of this. So APC is used to drive that reflectance at an angle into the cladding of the fiber instead of, essentially, a straight back reflectance. APC bulkheads also minimize "air gaps" between the 2 fibers connected to the bulkhead, which helps limit reflectance as well. UPC on the other hand is for a mostly traditional data connection, since it is a lot more tolerant of back reflectance. Things like IPTV will not see a difference between APC or UPC connections as it is a data stream. This is why inside a central office you will see UPC/Blue connections between routers/switches/softswitches. In most PON deployments that have an RF overlay, you will see that the OLT ports will be Blue for UPC connections with a fiber that heads over to a V-OLT that also has a Blue UPC connection. That V-OLT will also have a Green APC port for the video feed for ingress. Then there will be a Green APC port for egress into the PON splitter, since the V-OLT has combined the wavelengths from the "data" side and the "video" side together. For more information and inquiries, please feel free to send an email to vivien@sopto.com.