An evaluation of modelling of propagation using COMSOL for a singlemode-multimode-singlemode structure

This paper presents simulation models developed for investigating singlemode-multimode-singlemode (SMS) structures, with the intention of utilising precise nano-scale 3D printing to print the center-section of the structures modelled. The models allow the design of structures for use in SMS fiber sensors, replacing the silica fiber center-section structures commonly used, with 3D printed elements. The paper discusses the process of evaluating and validating COMSOL propagation models by comparison to existing reported results and proposes the use of SMS self-imaging length and the transmission spectra as useful metrics for model comparisons. Both 2D and 3D COMSOL models are developed, and both show good agreement in calculating self-imaging length with the other referenced models. In particular, the 3D model not only simulates the self-imaging length with high accuracy, but also shows good spectral agreement with the referenced models and an analytical calculation. In addition, results from previously published work by the group are used for comparison with the 3D COMSOL model.