An adapter includes an integrally-molded metal housing defining a first port axially aligned with a second port, each adapted to receive an optical connector plug having a cylindrical ferrule. A junction portion defines a cylindrical axial passage between the ports and has a first end adjacent the first port and a second end adjacent the second port. The first end of the junction portion has a ridge portion extending inwardly, thereby restricting a diameter of the passage at the first end. An alignment sleeve is disposed in the passage, the alignment sleeve having a diameter suitable for receiving a ferrule of each optical connector plug and axially aligning the ferrules to effect optical coupling of fibers contained in the ferrules. An end cap is disposed at the second end and is engaged with the junction portion to restrict the diameter of the passage at the second end, thereby securing the sleeve in the passage.