Laser Diode to Elliptic-Core Step Index Single Mode Fiber Excitation via Parabolic Microlens on the Fiber Tip: Prediction of Coupling Efficiency by ABCD Matrix Formalism

Abstract

We investigate theoretically the coupling optics involving laser diode and elliptic core step index monomode fiber via parabolic microlens on the fiber tip in absence of possible transverse and angular misalignments. By employing Gaussian field distributions for both the source and the fiber and also the derived ABCD matrix for parabolic microlens, we formulate analytical expressions for the concerned coupling efficiencies. Our formalism is very simple in comparison to the other existing methods involving cumbersome numerical integrations. Elliptic core single-mode fiber has already emerged as a potential candidate in polarisation conserving fiber optic sensor, coherent fiber optical communication etc.. The investigations have been performed for two different light emitting wavelengths of 1.3 µm and 1.5 µm for the said fibers. Therefore, such analysis which as per our knowledge is the first theoretical investigation, can also be treated as simple and novel prescription for choosing suitable parameters for the design of parabolic microlens on the tip of elliptic core step index fiber for optimum launch optics. In addition, this analysis will be useful in case of inherent non-circularity that may arise due to fabrication problem in circular core fiber and thereby generates interests among the experimentalists for verification and future investigations on parabolic microlens.