Fiber misalignment in silicon V-groove based optical modules

The use of anisotropically etched silicon optical benches (SiOB) and optical adhesives have attracted much attention for the low cost assembly of optical modules. In this paper, the effect of attachment process parameters (such as the amount of bulk adhesive, and the thickness/symmetry of the adhesive layer between the fiber and V-groove walls) on the alignment of the fiber with the laser diode assembled on SiOB, is studied. Finite element analysis (FEA) on the fiber displacement within the V-groove at a given temperature, increases significantly for different thicknesses of adhesive layers, present on either side of the fiber but does not change much with the total amount of adhesive in the module. Validation of the FEA data was accomplished by the use of in situ micro moiré interferometry, involving determination of the displacement of the centre of the fiber in the V-groove exposed to a temperature excursion ranging from room temperature to 125 °C. Maximum displacements of the fiber centre in the vertical and horizontal directions relative to the SiOB were found to range between 0.69-1.21 and 0.36-0.42 μm, respectively at 100 °C. The misalignment results obtained by moiré interferometry matched favorably with the finite element data. The simulation and experimental data in this study indicates that fiber misalignment due to temperature cycling can be reduced significantly if the fiber is located equidistant from the two inclined walls of the Si V-groove.