Optical interface cards, assemblies, and related methods, which may be suited for installation and use in antenna system equipment, are disclosed. In certain embodiments, an optical interface card (OIC) comprising a printed circuit board (PCB) having at least one optical sub-assembly (OSA) mounted to at least one first opening end of the PCB and extending into at least one opening and related methods are disclosed. In other embodiments, optical interface assemblies comprised of two OICs mounted together are disclosed. In other embodiments, a communications equipment enclosure including at least one fan configured to draw in air from a first side of the communications equipment enclosure into a lower plenum and across a plurality of communications components into an upper plenum to provide air cooling are disclosed. In another embodiment, a modular distributed antenna system assembly is disclosed.