Abstract: A connector for connecting two groups of optical fibers in axial alignment comprises a receptacle having therein a bore extending through it for holding therein two plugs, one on each side. The surface of the bore has two flat portions, one at each end. The portions of the plugs to be inserted into the bore also have flat portions shaped to contact the flat portions of the bore surface. The three interference bosses on the plugs are positioned such that after the plugs are inserted into the bore the bosses force the flat portion of the plug against the flat portion in the receptacle so that rotation of the plugs relative to the receptacle is prevented and the two plugs are substantially fixed in position relative to each other. Each plug assembly includes a ferrule having therein a passage and whose cross-section is triangular, square, polygonal or star-shaped. The plug assembly includes an insert shaped to press fit into the passage forming triangular spaces between the insert and the passage surface.