Coaxial Transmitter Optical Sub-Assembly Laser Welding Mechanism and Process Research

As an indispensable packaging technique for transmitter optical sub-assemblies (TOSAs), laser welding joins optical fibers and focusing lenses and exerts a decisive influence on the output optical power and long-term reliability of optoelectronic components. This research focuses on optimizing the laser welding process for 2.5 G coaxial TOSA packages. A systematic investigation is carried out to quantify the influences of weld microstructure, assembly clearance between the fiber adapter and laser housing, and laser beam focal position on three characteristic indexes: post-weld longitudinal displacement, optical power attenuation, and tensile force. Microstructural observations demonstrate that columnar grains dominate the fusion zone, developing rapidly in the direction perpendicular to the solid–liquid interface at the weld boundary. A favorable process window is determined via parametric experiments: laser energy of 2.5 J, assembly clearance of 20–60 μm, and a focal position of roughly −200 μm. This combination yields minimized post-weld displacement and optical power loss without compromising mechanical robustness. The outcomes advance the welding accuracy and structural integrity of TOSA packages and provide implementable guidance for the industrial development of laser-welded optoelectronic assemblies.