Key Takeaways

• Researchers have demonstrated the effectiveness of glass-epoxy-based polymer waveguides for co-packaged optics (CPO) systems.
• These waveguides feature low polarization-dependent loss and low differential group delay, enhancing optical signal stability.
• Experiments showed that the waveguides are resilient under high-power conditions, making them suitable for next-generation optical communication.

Advancements in Co-Packaged Optics Technology

Co-packaged optics (CPO) technology integrates photonic integrated circuits (PICs) with electronic integrated circuits (EICs), such as CPUs and GPUs, on a single platform. This setup has the potential to significantly improve data transmission efficiency in data centers and high-performance computing environments. Reliable laser sources are essential for CPO operation, and while integrated laser sources provide dense integration, they often face reliability issues. Consequently, researchers are exploring external laser sources (ELS) that can enhance system reliability.

A recent study led by Dr. Satoshi Suda from the National Institute of Advanced Industrial Science and Technology in Japan has investigated the performance of polymer waveguides based on glass-epoxy substrates. These waveguides have emerged as a promising solution for transmitting laser signals from external sources to photonic circuits.

The research team fabricated single-mode polymer waveguides measuring 11 mm in length, using direct laser writing techniques on FR4 glass-epoxy substrates. The waveguides were designed with core dimensions of 9.0 µm × 7.0 µm, aligning well with standard single-mode fibers. The waveguides exhibited low polarization-dependent loss (PDL) and low differential group delay (DGD), contributing to stable signal transmission and minimal distortion.

The evaluation included measurements of the waveguides’ performance across eight samples, which showed consistent insertion loss and mode field dimensions. Such efficiency in optical interconnects indicates they are suitable for CPO systems relying on external laser sources.

Another critical aspect of the research was the polarization extinction ratio (PER), which measures waveguides’ capability to sustain specific polarization for transmitted signals. The team found a high PER of over 20 dB across all wavelengths within the CWDM4 standard, including 1271, 1291, 1311, and 1331 nm, meeting the OIF specifications for ELS-based CPO systems.

Further tests on the glass-epoxy waveguides revealed their resilience under high-power conditions. They maintained performance standards even after six hours of continuous operation, with minimal heat generation. This stability was observed with ELS provided by Furukawa Electric Co., Ltd., underscoring the practicality of these waveguides for demanding CPO applications.

Dr. Suda remarked, “Polymer waveguides show strong potential for use in demanding CPO systems. We, therefore, evaluated the fundamental optical properties of the single-mode polymer waveguides on the glass-epoxy substrate.” The findings from this research signify a meaningful contribution to the development of high-density and high-capacity optical communication technologies, marking a significant step forward in optical signal transmission reliability.

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