The development of low-loss polymer optical waveguides is the main objective of this project to enhance the high bandwidth density wiring for HPC systems. Optically transparent polymer materials must be used to integrate optical wiring elements onto printed circuit boards instead of traditional electrical cabling. For the board levels of high-performance computing systems, we intend to design and develop SI single-mode core polymer MMI-based Y-branch and MZI couplers in this research. The MMI-based Y-branch coupler used in this project has a Y-branch structure, with one input connected to the two S-bend elements and two MMI sections to provide four outputs. The splitter has been used as a switch as well. We also intend to create polymer MZI waveguides that utilize the MMI coupling on the two arms, which is thermally reliable and compact, used as an electro-thermo-optic Mach Zehnder Interferometer-based modulator. The beam propagation method (BPM) will be used to examine the optical characteristics of these two innovative devices, particularly the near-field pattern, polarization loss, and excess loss. Therefore, these MMI-based Y-shaped couplers and MZI waveguides could be novel devices to improve the wiring density and high-bandwidth performance for PCBs and PICs of high-performance computing systems.