Structural Optimization of an Optical 90 Degree Hybrid Based on a Weaklyguided 4x4 Multimode Interference Coupler Using a Parallelized Real-coded Micro-genetic Algorithm
Keywords:Beam-propagation method, finite element method, genetic algorithm, multimode interference coupler, optical waveguides, parallel computation
The optimal design of a 4x4 multimode interference (MMI) coupler as an optical 90° hybrid based on a weakly-guided optical waveguide was considered. Seven geometrical parameters of a 4x4 MMI coupler were optimized by a real-coded micro-genetic algorithm, and parallelized using a message-passing interface. The beam-propagation method was used to evaluate the fitness of the MMI coupler in the optimization process. The optimized 4x4 MMI coupler showed a common-mode rejection ratio greater than 28.9 dBe and a phase error less than 2.52° across a wavelength range of 1520 to 1580 nm, which satisfied typical system requirements. The optimization process was executed on a Beowulf-style cluster comprising five identical PCs, and its parallel efficiency was 0.78.
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