Beam locking for free space optical communication systems using vertical-cavity surface-emitting laser arrays. The method includes: transmitting a communication beam from a light source of a first free space optical unit to a detector arranged proximate to a second FSO unit, the second FSO unit having reflective elements; transmitting one or more alignment beams from the light source to the second FSO unit; reflecting the one or more alignment beams or one or more portions thereof from the one or more reflective elements; detecting the reflected one or more alignment beams or one or more portions thereof at a light sensor; and determining whether the first FSO unit is aligned with the second FSO unit or whether the at least one communication beam is affected by one or more environmental conditions based on the detection of the reflected one or more alignment beams or the one or more portions thereof.