Optical coupling and alignment tolerances in optoelectronic array interface assemblies

A novel analytic beam propagation approach to multimode coupling modeling is presented which models mode power and phase distributions from first principles (unlike ray-tracing.) Coupling between axially misaligned multimode fibers has been simulated and compared with measurements. The relationships between optical coupling and fabrication and assembly tolerances have been studied for a generic laser diode array-to-optical fiber array coupler. Sources for lateral and transverse misalignment have been identified and related to variations in micromachining, components, assembly and thermo-mechanical stresses. Assessment of these misalignment sources leads to worst case laser diode-to-optical fiber transverse and lateral misalignments of approximately 2.8 μm for single-mode coupling and 4.1 μm for multimode coupling. These values indicate that this laser array interface, in its present form, is suitable for multimode fibers but not single-mode fibers