A wafer-level packaged optical subassembly includes: a substrate element, the substrate element including a top layer and a base layer being bonded with the top layer; a top window cover being bonded with the top layer of the substrate element; and a plurality of active optoelectronic elements disposed within the substrate element. At least one primary cavity is defined in the substrate element by the top layer and the base layer, and configured for accommodating the active optoelectronic elements. A plurality of peripheral cavities are defined around the at least one primary cavity as alignment features for external opto-mechanical parts.