Effect of temperature cycling on angular alignment in add/drop filter-module packaging

Abstract

The thermally-induced, fiber-alignment shifts of ferrule-solder-ferrule (FSF) joints in add/drop filter-module packaging for multiplexer/demultiplexer applications have been studied experimentally and numerically. From experimental measurements of the module-insertion loss difference (0.3 dB) with and without temperature cycling, FSF angular-tilt misalignments of up to 0.05° were found after undergoing 42 temperature cycles. The effects of an imperfect soldering process along the two ferrules during the packaging of an add/drop filter module on the angular-tilt misalignment has been explored in this study. An elastic-plastic finite-element method (FEM) was performed to evaluate the variation of thermal stresses, the distribution of residual stresses, and the angular-tilt misalignment of the FSF joints. Experimental measurements of the FSF angular-tilt misalignment were in good agreement with the FEM calculations. The major angular-tilt misalignments of FSF joints in add/drop filter-module packaging during temperature cycling may come from the localized plastic-solder yielding introduced by the local thermal-stress variation and the redistribution of the residual stresses within the solder. The FSF angular-tilt misalignment and, hence, fiber-alignment shift of the add/drop filter module under temperature-cycling tests can be reduced significantly if a perfect soldering process along the two ferrules can be fabricated.