Fiber optic interface devices (20, 320) for electronic devices (300) are disclosed. A plug-type fiber optic interface (20) has an axially moveable multi-fiber ferrule (100) that supports optical fibers (52) or a combination of optical fibers and gradient-index lenses (600). A resilient member (150) serves to provide the ferrule with forward-bias and rear-bias positions relative to a recessed front end (22) of a housing (21). A fiber optic interface assembly (570) that includes mated plug and receptacle fiber optic interface devices (20, 320) is also disclosed.