Fiber optic adapter, sometimes also named coupler, is a small device used to connect two fiber optic connectors in the fiber optic lines. The adapters offer more precise alignment of the tips of the connectors (ferrules), and ensure light sources to be transmitted at most and with lower loss.
Available in a variety of interfaces including FC, SC, ST, LC, MU, E2000, MTRJ, MPO, MTP, etc. Most of the options are offering with a choice of zirconia or phosphor bronze sleeves for singlemode or multimode applications.