What is fiber optic network adapter?"); display: inline-block; height: 24px; width: 24px; margin-top: -1px; transform: rotateZ(-180deg);">A fiber optic adapter or coupler is a special connector designed to mate or connect two ends of a fiber optic cable with high precision. The adapter uses a simple design: the ends of two separate fiber optic cables with fiber optic connectors fit into two slots opposite each other.