Specifically designed for multimode fibers (50µm or 62. 5µm core), these adapters facilitate efficient light coupling across shorter distances using wavelengths like 850nm or 1300nm. Ideally suited for Datacom and Telecom applications in densely packed patch panels. Discover Amphenol FOP's ST and STII fiber optic adapters-engineered for high-density telecom/datacom. A fiber-optic adapter — sometimes called a coupler or bulkhead coupler — is a passive mechanical interface that mates and aligns two terminated optical fibers (i., two fiber connectors) such that light can reliably pass from one to the other with minimal insertion loss and maximum return loss. ST Adapters are essential optical connectors used to join two ST-terminated fiber optic cables. Designed with a. Leviton's ST simplex adapters are available with metal housing and a precision zirconia ceramic split sleeve for providing low loss fiber connections over high and low-temperature extremes.