US Patent 9470847 Polarization maintaining connectors

A connector comprising an outer housing having a first keying element, an inner housing at least partially disposed in the outer housing and having second and third keying elements, the second keying element cooperating with the first keying element to align angularly the inner housing with the outer housing, a ferrule assembly at least partially disposed in the inner housing and having a ferrule and fourth and fifth keying elements, the fourth keying element cooperating with the third keying element to align angularly the ferrule assembly with the inner housing, an alignment member receiving at least a portion of the ferrule assembly, the alignment member having a sixth keying element to cooperate with the fifth keying element to align angularly the ferrule assembly with the alignment member, and wherein the clearance between the fifth and sixth keying elements is less than that between the first and second keying elements, and between the third and fourth keying elements.