High-Power Stability and Reliability of Polymer Optical Waveguide for Co-Packaged Optics

This paper explores the fundamental optical characteristics and high-power handling capabilities of single-mode polymer waveguides fabricated on glass-epoxy substrates for co-packaged optics (CPO) utilizing external laser sources (ELS). The waveguides exhibit low polarization-dependent loss (PDL) of less than 0.5 dB and low differential group delay (DGD) of less than 0.2 ps in the O-band, along with excellent uniformity across eight fabricated samples. Key parameters such as insertion loss and mode field dimensions demonstrated extremely small variations, ensuring consistent performance across eight waveguides. The polarization extinction ratio (PER), a critical metric for evaluating waveguide performance in ELS-based systems, was measured at all wavelengths within the CWDM4 standard, specifically at 1271, 1291, 1311, and 1331 nm. A high PER of over 20 dB was achieved in all waveguides and at all wavelengths, indicating stable polarization control. Additionally, high-power reliability testing was conducted under continuous-wave optical input of +20 dBm, demonstrating excellent input-output linearity and no measurable power degradation after 6 hours. Thermal analysis showed a minimal temperature rise of approximately 4.4 °C under these conditions, consistent with theoretical predictions, highlighting the robustness of the waveguides under high-power conditions. These results confirm the polymer waveguides are suitable for demanding ELS-based applications, providing reliable and efficient solutions for next-generation high-density and high-capacity optical communication systems, such as data centers and high-performance computing environments.