In this beginner-friendly guide, we'll explain what it is, why the “APC” matters, the different types you can buy, how to select the right model, and how to install and test it correctly. What is an SC/APC Fiber Optic Adapter?Fiber optic adapters are small but essential components that ensure precise alignment between connectors. In this tutorial. If you work with single‑mode optical networks—FTTH, PON, CATV, 5G fronthaul—you will run into the SC/APC fiber optic adapter (sometimes called an SC/APC coupler) almost immediately. However, setting up a fiber optic connection to your router can seem daunting if you're unfamiliar with the process.