Fiber Alignment Shifts Research Articles

Experiment and Simulation on Reduction of Postweld Shift on Butterfly-Type Laser Module by Nd:YAG Laser Welding and Separated Dual Clips

The experiment and simulation on reduction of postweld shift caused by laser welding on a butterfly-type laser module package employing Nd:YAG laser welding and separated dual clips are demonstrated in this study. Based on the measurement of fiber tip position, the direction and quantity of fiber alignment shift caused by laser welding joining are quantitatively measured, and the postweld shift during laser welding also can be compensated by separated dual clips with pre-compensation. The experimental results also show that the coupling efficiency can be regained up to 79%–95% of optimum coupling power. The simulation results show the regained coupling efficiency of 81%–96% and also match quite well the experimental results in trends.

A Quantitative Postweld Shift Measurement and Compensation Technique in Butterfly Laser Module Packages

A quantitative postweld shift (PWS) measurement and compensation technique employing a high-magnification camera with image capturing system (HMCICS) in butterfly-type laser module packages is investigated. The results show that the direction and magnitude of the fiber alignment shifts induced by the PWS in laser-welded butterfly-type laser module packaging can be quantitatively determined and compensated. The measured coupling powers in laser module packages after welding and compensation were clearly confirmed the measured fiber shifts that determined by the translational and rotational parameters. Therefore, the fiber shifts due to the PWS could be realigned back closer to their original optimum position after applying welding compensation, and hence the coupling powers loss due to the PWS could be regained. In comparison with previous studies of the PWS compensation by the well-known mechanical adjustment through a qualitative estimation technique, this HMCICS technique has successfully provided the mechanical adjustment through a quantitative compensation to the effect of the PWS on the fiber alignment shifts in butterfly-type laser module packages. The reliable butterfly-type laser modules with high yield used in lightwave transmission systems can be developed and fabricated.

Investigation and Comparison of Postweld-Shift Compensation Technique in TO-Can- and Butterfly-Type Laser-Welded Laser Module Packages

The postweld-shift (PWS) compensation techniques employing a laser displacement meter (LDM) in the transistor outline (TO)-Can-type laser-welded laser module package and a high-magnification camera with image capturing system (HMCICS) in the butterfly-type laser-welded laser module packages are quantitatively investigated and compared. The results show that the fiber alignment shifts due to the PWS can be aligned back closer to their original optimum position after applying the proposed compensation techniques, and hence the coupling powers loss due to the PWS could be regained significantly. Comparing with the measured coupling power and the PWS, the results show that the PWS are in the ranges of 0.2-1.6 mum and 2.1-4.2 mum for the TO-Can- and the butterfly-type laser packages, respectively. The reason for having a larger PWS in the butterfly laser package is that the fiber ferrule is not solidly constrained in the vertical direction. In this paper, a coupled thermal-elasto-plasticity model of a finite-element method (FEM) analysis is employed to evaluate the PWS in the TO-Can- and the butterfly-type laser module packages. The simulated results are in good agreement with the measured results and these show that the PWS in the butterfly-type laser packages are larger than those in the TO-Can packages. A combination of the experimental and numerical results has provided a practical design guideline for fabricating reliable and high-yield laser-welded TO-Can- and butterfly-type laser module packages for use in lightwave communication systems

Adhesive Joint Design for Minimizing Fiber Alignment Shift During UV Curing

In fiber-optic device packaging using UV curable adhesive bonding, the curing process often causes fiber alignment shift-distortion of the already aligned fiber-optic setups, and thus reduce the assembly yield. A new method for the adhesive joint design for minimizing fiber alignment shift during adhesive curing is reported in this paper. It is demonstrated that for any adhesive, the bonding joint can be designed to alleviate the alignment shift, regardless of adhesives used. The approach provides guideline for high yield and low-cost assembly of fiber-optic devices using adhesive bonding

Postweld-shift-induced fiber alignment shifts in laser-welded laser module packages: experiments and simulations

The fiber alignment shifts induced by the postweld shift (PWS) in laser-welded transistor outline (TO)-Can-type laser module packages were studied experimentally and numerically. The PWS-induced fiber alignment shifts were quantitatively determined by four geometrical parameters, namely: 1) the lateral shift (r); 2) the position angle (/spl alpha/); 3) the swing angle (/spl theta/); and 4) the tilt angle (/spl psi/). The measured coupling powers in laser module packages before welding, after welding, and after a welding compensation clearly confirmed with the measured fiber alignment shifts determined by the dominant parameters of the r and /spl alpha/ that the fiber shifts due to the PWS could be realigned back closer to their original optimum position after applying a welding compensation, and, hence, the coupling power loss due to the PWS could be regained. A coupled thermal-elastoplasticity model of finite-element-method (FEM) analysis was performed to evaluate the effects of PWS on fiber alignment shifts in laser module packages. The measured fiber alignment shifts determined by the dominant parameters of the r and /spl alpha/ were in good agreement with the numerical calculation of the FEM analysis. In this study, the combination of the experimental and numerical results have significantly provided a practical design guideline for fabricating reliable laser-welded TO-Can-type laser module packages with a high yield and high performance for use in low-cost lightwave transmission systems.

A novel fiber alignment shift measurement and correction technique in laser-welded laser module packaging

A novel measurement and correction technique employing an ultra-high-precision laser displacement meter (LDM) with a 20-nm resolution to probe the postweld-shift (PWS)-induced fiber alignment shifts in laser-welded laser module packaging is presented. The results show that the direction and magnitude of the fiber alignment shifts induced by the PWS in laser-welded laser module packaging can be quantitatively determined by four parameters: the lateral position (r), the position angle (/spl alpha/), the swing angle (/spl theta/), and the tilt angle (/spl psi/). Further studies show that the deformation of the lateral shift and the position angle are the dominant mechanisms that determine the fiber alignment shifts induced by the PWS. This clearly indicates that the PWS can be quantitatively corrected timely by applying a single weld spot on the negative lateral shift and the position angle to compensate for the fiber alignment shifts. In comparison with previous studies of the PWS correction by a qualitatively estimated technique, this LDM technique has significantly provided an important tool for quantitative measurement and correction to the effect of the PWS on the fiber alignment shifts in laser-welded laser module packaging. Therefore, the reliable laser modules with high yield and high performance used in low-cost lightwave transmission systems may be developed and fabricated.

An Optimum Approach for Reduction of Fiber Alignment Shift of Fiber-Solder-Ferrule Joints in Laser Module Packaging

The results of experimental and numerical investigations leading to an optimum approach for the reduction of fiber alignment shift of fiber-solder-ferrule (FSF) joints in laser module packaging under temperature cycling test is presented. Using a novel image capture camera system as a monitor probe and the Sn -based solders as bonding materials, we have achieved the minimum fiber eccentric offsets of 8 and 20 /spl mu/m in FSF joints with the PbSn and AuSn solders, respectively. After a 500-temperature cycling test, the fiber alignment shifts for these small initial fiber eccentric offsets of FSF joints were found to be 0.7 and 0.3 /spl mu/m with the PbSn and AuSn solders, respectively. The measured fiber shifts were in good agreement with the numerical results of the finite-element method (FEM) analysis when both the residual stresses and the creep deformation within the solder were considered. This study have demonstrated that by soldering the fiber near to the center of the ferrule, and hence minimizing the fiber eccentric offset, the fiber alignment shifts of FSF joints in laser diode module packaging under temperature cycling test can be reduced significantly.

Fiber-alignment shifts in butterfly laser packaging by laser-welding technique: Measurement and finite-element method analysis

The post-weld shift (PWS)-induced fiber-alignment shifts of fiber-ferrule clip (FFC) joints in butterfly laser packaging by using laser-welding techniques and a high-magnification, video-probe camera system were studied experimentally and numerically. The measured results show that the fiber shifts of FFC joints with a 5-μm gap between the clip and ferrule exhibited shifts less than that without a gap. This suggests that the 5-μm gap design may be more suitable for FFC joints in laser packaging. The experimental measurements of fiber shifts in FFC joints were in reasonable agreement with the numerical calculations of the finite-element method (FEM) analysis. The major fiber-shift formation mechanisms of FFC joints in the laser-welding process may come from the mismatch of the thermal expansion coefficient, the solidification shrinkage, and the residual stresses within the FFC joint, but solidification shrinkage is the dominant cause. This study demonstrates that the FEM is an effective method for predicting PWS-induced fiber-alignment shifts in laser-module packaging.

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

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.

Fiber alignment shift formation mechanisms of fiber-solder-ferrule joints in laser module packaging

The fiber alignment shifts of fiber-solder-ferrule (FSF) joints in laser module packaging under temperature cycle testing using PbSn and AuSn solders are studied experimentally and numerically. The measured results showed that the fiber shifts of FSP joints with the hard AuSn solder exhibited shifts two times less than that with the soft PbSn solder. This suggests that the hard solder may be more suitable for FSF assembly than the soft solder. The results also showed that fiber shifts increased as the temperature cycle number and the initial fiber eccentric offset increased. The experimental measurements of fiber shifts were in good agreement with the numerical calculations of the finite-element method analysis. The major fiber shift formation mechanisms of FSF joints in temperature cycling may come from the localized plastic solder yielding introduced by the local thermal stress variation, the redistribution of the residual stresses, and the stress relaxation of the creep deformation within the solder. Furthermore, the stress relaxation of creep deformation in solder with either 21% (PbSn solder) or 5% (AuSn solder) may have significant influence on the fiber shifts. This study has provided an optimum approach for reduction of the fiber alignment shift of FSF joints in laser module packaging under temperature cycle testing, which is to solder the fiber near to the center of the ferrule and to select the AuSn hard solder.

Reduction of fiber alignment shifts in semiconductor laser module packaging

The thermally induced fiber alignment shifts of fiber-solder-ferrule (FSF) joints in laser module packaging have been studied experimentally and numerically. From direct measurements of the metallographic photos with and without temperature cycling, fiber displacement shifts of up to a 0.8 /spl mu/m were found after undergoing 500 temperature cycles. Experimental results show that the fiber shifts increase as the temperature cycle number and the initial fiber eccentric offset increase. The major cause of fiber shift may come from the plastic solder yielding introduced by the thermal stress variation and the redistribution of the residual stresses during temperature cycling. 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 FSF joints. Experimental measurements were in reasonable agreement with the numerical calculations. Both results indicate that the initial offset introduced in the fiber soldering process is a key parameter in causing the thermally-induced fiber shift of FSF joints in laser module packaging. The fiber shift, and hence fiber alignment shift under temperature cycling tests can be reduced significantly if the fiber can be located close to the center of the ferrule.