The design of passive photonic devices based on geometry optimization can lead to energy-efficient, small-footprint, and fabrication-ready geometries. In this work, we propose an angle-based parametrization method to optimize Y-junction splitters based on multimode interferometers. The selected figure of merit was the transmittance in the SCL and OESCL optical fiber communication bands. The performances of three optimization methods were compared: (i) particle swarm optimization (PSO), (ii) genetic algorithm (GA), and (iii) the covariance matrix adaptation-evolution strategy (CMA-ES). The results show that CMA-ES parametrization produces similar transmittance results (≤1.5% of difference) to PSO in the first 40 generations. The CMA-ES results are identical in the SCL (1460–1625 nm) and OESCL (1260–1625 nm) bands, whereas the GA and PSO executions are slightly different in terms of the rate and similarity of the figure of merit.