Reduction of fiber alignment shift in add/drop filter module packaging

The influence of solder solidification on fiber alignment shift in an add/drop filter module packaging is studied experimentally and numerically. A finite-element method (FEM) analysis was performed to evaluate the variation of thermal stresses, the distribution of residual stresses, and fiber shifts of the ferrule-solder-ferrule (FSF) joints in add/drop filter module. Both experimental and numerical results show that the dominant fiber alignment shift in packaging of an add/drop filter module is the ferrule eccentric offset increase introduced by the solder solidification shrinkage during the solder process of FSF joints, resulting in the angular tilt misalignment between two fiber collimators. The fiber alignment shift under solder solidification can be reduced significantly if the two ferrules can be located close to the center of the tube and the solder distribution is uniform along the two ferrules.