In one embodiment, an optical subassembly includes a housing, a ball lens, a constraining insert, and a ball lens constraint. The housing includes a fiber receptacle formed in a first end of the housing and a second receptacle formed in a second end of the housing opposite the first end. The fiber receptacle and second receptacle define a cavity through the housing from the first end to the second end of the housing. The ball lens and the constraining insert are disposed within the cavity. The ball lens constraint is configured to cooperate with the constraining insert to constrain the ball lens in three dimensions within the cavity.
