PRODUCTS

As AI data centers continue to grow, the demand for faster and more energy-efficient data transmission is increasing rapidly. Traditional electrical interconnects are facing growing limitations in bandwidth, power consumption, and latency. This is one reason why Co-Packaged Optics (CPO) and silicon photonics are attracting increasing attention as next-generation interconnect technologies. But there is a challenge that is often overlooked: CPO may be ready for commercialization, but is CPO testing ready for mass production? According to TrendForce, testing remains one of the key bottlenecks as CPO moves from the laboratory toward volume production. TSMC’s COUPE platform is also targeting volume production in 2026, further accelerating the development of the CPO ecosystem. What Makes CPO Testing So Difficult? Unlike traditional electronic IC testing, CPO combines electrical and optical technologies in the same package. A typical CPO architecture integrates a Photonic Integrated Circuit (PIC) with an Electrical Integrated Circuit (EIC). The combined component is often referred to as an Optical Engine (OE). The PIC may include: Optical couplersModulatorsPhotodetectorsOptical filtersOptical waveguides This means testing is no longer just about electrical performance. Engineers also need to measure optical parameters such as: Insertion Loss (IL)Polarization-Dependent Loss (PDL)ResponsivityWaveguide propagation lossOptical crosstalk The combination of electrical, optical, and optoelectronic testing makes CPO testing significantly more complicated than conventional IC testing. The Alignment Problem One of the biggest challenges is optical alignment. Light needs to travel from an external optical fiber into an extremely small optical waveguide. The difference in physical size is enormous. According to TrendForce, the cross-sectional area of a single-mode fiber core is approximately 78.5 µm², while the optical waveguide can be around 0.099 µm². That means the fiber core can be hundreds of times larger than the waveguide. Even a small positioning error can result in significant coupling loss. This is why CPO testing requires extremely precise alignment, together with advanced optical probes, machine vision, and automated positioning systems. Today, some of these processes still involve significant manual operations. TrendForce estimates that 100% inspection of a single PIC can take more than 100 seconds, creating a major challenge for high-volume manufacturing. Four Key Stages of