Investigation of the Effects of Alignment Errors on Coupling Efficiency in Lens-Based Coupling of Polarization-Maintaining Fibers

The fiber mode field overlap integral method is employed to analyze the influencing factors of coupling efficiency, as well as the effects of axial and radial alignment errors on coupling efficiency under different relative apertures of coupling lenses. The results indicate that there exists an optimal relative aperture of the coupling lens that maximizes coupling efficiency; however, at this optimal point, coupling efficiency is more susceptible to radial errors. Regarding axial and radial errors, when the relative aperture of the coupling lens is at its optimal value, the tolerance for alignment errors is minimal. Conversely, when the relative aperture exceeds the optimal value, both coupling efficiency and tolerance for alignment decrease. When the relative aperture is less than the optimal value, the requirement for installation accuracy decreases while the tolerance becomes larger. The trend of the simulation results aligns with the experimental data. This study provides instructive significance regarding the trade-off between coupling efficiency requirements and alignment accuracy in the design of actual polarization-maintaining fiber coupling systems.