, LC-LC, SC-SC) for same-type connectors. Bare fiber adapters are ideal for temporary or emergency fiber testing applications. A fiber optic coupler works by precisely. A fiber optic adapter (or fiber coupler) is a passive component used to join and align two optical connectors. It plays a key role in maintaining core-to-core alignment, allowing optical signals to pass through with minimal insertion loss and stable performance. They come in different versions, including simplex, duplex, and quad, depending on the number of fibers they can connect.