Bringing Down Test Costs for Co-Packaged Optics
Co-packaged optics (CPO) is moving from research labs into volume manufacturing as AI and hyperscale data centers demand higher bandwidth at lower power. Yet one of the biggest barriers to adoption remains test cost β a challenge that is now drawing focused engineering attention across the semiconductor supply chain.
Why CPO Test Is So Expensive
CPO integrates photonic integrated circuits (PICs) alongside electrical ICs in a single package, eliminating the long electrical traces that dominate power consumption in conventional pluggable transceiver architectures. That integration delivers compelling power and latency benefits, but it also compounds test complexity:
- Mixed-signal and optical test in one flow. Each package must be validated for both electrical and optical performance, often requiring specialized equipment and calibration.
- Known-good-die requirements. Because assembled CPO packages are difficult and costly to rework, every PIC and electrical die must be verified before integration.
- Wafer-level optical probing. Testing optical structures at wafer level demands precision probing, alignment, and stable light coupling β all of which add time and cost per device.
- Limited parallelism. Optical test setups historically test fewer devices simultaneously than high-throughput electrical test, reducing throughput per tester hour.
Strategies for Cost Reduction
As of 2026, the industry is converging on several approaches to bring CPO test economics in line with volume manufacturing targets:
1. Shift Test Earlier in the Flow
Moving more test coverage to wafer-level and known-good-die screening reduces the cost of scrapping or reworking fully assembled packages. Early defect detection is especially valuable given the high value of each finished CPO module.
2. Design for Test (DFT) in Photonics
Photonic DFT β including on-chip monitors, loopback structures, and built-in test access β is maturing rapidly. Embedding testability into PIC designs reduces dependence on external optical instrumentation and shortens test time.
3. Test Parallelism and Automation
New probe card and test cell architectures are increasing the number of optical channels tested in parallel. Automation of fiber alignment and calibration is also cutting per-device test time significantly compared with manual or semi-automated setups.
4. Standards and Ecosystem Alignment
Industry consortia and standards bodies are working to define common test interfaces and methodologies for CPO, which should reduce redundant test development and improve equipment reuse across suppliers.
5. Co-Optimizing Package and Test Design
Treating test access as a first-class constraint during package architecture definition β rather than retrofitting it afterward β is proving one of the most effective levers for controlling cost.
Outlook
CPO adoption timelines depend as much on test economics as on optical performance. With AI-driven demand accelerating in 2026, the companies that solve test cost and throughput challenges first will be best positioned to scale co-packaged optics into mainstream data center deployment.