A parallel optical communications device is provided that has an OSA that includes at least one heat dissipation block having a slot formed in a lower surface thereof that contains a weldable insert. Likewise, an upper surface of the mounting device of the ESA has at least one slot formed therein that contains a weldable insert. After the OSA is placed in contact with the ESA and optically aligned with the ESA, the OSA is secured to the upper surface of the mounting device of the ESA by welding together the respective weldable inserts contained in the respective slots in the OSA and in the mounting device of the ESA. The welding process results in an extremely strong welded joint between the OSA and the ESA that prevents relative movement between the OSA and the ESA if external forces that are exerted on the OSA and/or on the ESA.