1. From 2D to 2.5D/3D Integration

Extreme I/O density is pushing traditional organic substrates to their practical limits. As bandwidth increases, signal routing complexity, warpage control, and power delivery integrity become progressively harder to manage within 2D approaches.

In response, CPO architectures are moving toward 2.5D and 3D integration strategies. Silicon bridges, fine-pitch redistribution layers (RDL), and advanced interposer approaches are becoming central to enabling this transition. These technologies are structural enablers that directly influence performance, signal integrity, and long-term manufacturability. The shift reflects a broader evolution in how advanced systems are physically constructed.

2. Growing Interest in Glass Substrates

At the same time, glass substrates are drawing increased attention within CPO architectures.

Glass offers panel-scale economics, strong dimensional stability, and fine-pitch through-glass via (TGV) capability. These attributes directly address routing density and warpage challenges. Importantly, they do so without incurring the full cost burden typically associated with silicon interposers. As a result, substrate selection is becoming a system-level architectural decision rather than a materials substitution exercise.

3. Optical Engines as Heterogeneous Systems

Beyond substrates and interconnects, the optical engine itself must be viewed as a heterogeneous system. CPO is not simply optics placed next to an ASIC.

The optical engine is a PIC + EIC assembly. Bonding topology, parasitics, thermal paths, alignment strategy, and test methodology all directly affect power efficiency and signal integrity. These variables introduce integration dependencies across substrate, interconnect, and optical assembly layers. Each layer adds complexity, and each requires early evaluation to avoid downstream performance and yield limitations.

These shifts are not isolated technical adjustments; they collectively redefine how high-performance systems must be designed.