Analytical-Based Mode Group Division Multiplexer Design Using Gaussian Beam Generalized Launch

The optical power coupling coefficient serves as a pivotal metric for elucidating mode power distribution within mode group division multiplexers. This paper derives closed-form analytical expressions to calculate the coupling coefficient of Gaussian beams into a graded-index multimode fiber. Leveraging the inherent computational efficiency of analytical solutions over numerical counterparts, we introduce an efficient design methodology for mode group division multiplexers. This innovative approach hinges on generalized launch conditions and employs a multiple-population genetic algorithm for optimal solutions. The achieved results underscore the efficacy of our approach, as evidenced by the <tex-math notation="LaTeX">5× 5</tex-math> and <tex-math notation="LaTeX">6× 6</tex-math> mode-group division multiplexers operating at 1310 nm. These multiplexers showcase satisfying alignment stability, enabling to curtail the degradation of channel insertion loss to a maximum of 0.03 dB. The proposed conditioned-launch-based multiplexer, enhancing fiber transmission capacity, offers the distinct advantages of simplified fabrication processes and subsequently reduced financial costs.