Numerical Design of a Passive Quadrature Phase and Power Splitter Using 2×2 RI-MMI Couplers with a Fixed Phase Shifter for QPSK and Multicarrier OFDM Applications

EDA LAB, Faculty of Electrical Engineering 1, Posts and Telecommunications Institute of Technology Hanoi, Vietnam This email address is being protected from spambots. You need JavaScript enabled to view it.
EDA LAB, Faculty of Electrical Engineering 1, Posts and Telecommunications Institute of Technology Hanoi, Vietnam This email address is being protected from spambots. You need JavaScript enabled to view it.
Advanced Institute of Science and Technology-The University of Danang Danang, Vietnam This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

We present an optimized design of a 1:4 quadrature phase and power splitter implemented on silicon photonic waveguides. The device operates under the restricted interference regime to achieve a compact footprint. The photonic circuit employs cascaded 2×2 RI-MMI couplers with two spans and a fixed 90-degree phase shifter in one arm, ensuring uniform quadrature phase differences among the output ports. Using 3D-BPM numerical simulations, the optimal MMI length is determined to be 35.4 µm, with a phase shifter length of 26 µm. The simulation results confirm outstanding optical performance, exhibiting low excess loss (<4.6 dB) across a broad spectral range (1500–1600 nm). The device ensures excellent power uniformity across all output ports, with a maximum balance factor of 13 dB, guaranteeing reliable and stable operation. Additionally, the output signals maintain precise 90-degree phase shifts across the four ports (1, 2, 3, and 4), as validated by the signal constellation diagram. These results demonstrate the superior suitability of the proposed device for advanced optical signal processing applications, including QPSK-loaded modulators, multicarrier phase-coded OFDM, optical phasors, and multiphase local oscillators, offering a robust and high-precision solution across multiple wavelength bands.