SEMICON 2025 Silicon Photonics Summit | SENKO: Detachable Fiber-to-Chip Connectors and Seat Technology

Introduction

As AI compute demand keeps rising, silicon photonics (SiPh) and co-packaged optics (CPO) have become key technologies for data centers and AI infrastructure. While the industry broadly agrees on the advantages of silicon photonics and CPO, many detailed challenges remain in real-world deployment, and the most important of them is how fiber connects to the chip.

At the SEMICON 2025 Silicon Photonics Summit, SENKO focused on the detachable fiber-to-chip connector and presented its patented Seat technology to address challenges in alignment accuracy, repeatability, reliability and test cost.

Content

1. Why Detachable Connections?

• Bandwidth demand in the AI era: CPO offers power and cost advantages and is expected to enter real deployment in 2026–2027.

• Challenge: silicon photonics modules require not only chip-level optical coupling but also full system connectivity across the front panel, ELSFP and backplane.

• Solution: detachable connectors reduce packaging and test difficulty and support high-volume manufacturing.

2. Core Challenges of Detachable Connections

SENKO noted that four major problems must be overcome to make detachable fiber-to-chip connections truly viable:

1. Optical path setup: ensuring low-loss transmission between fiber and chip.

2. Precision alignment: sub-micron alignment accuracy must be maintained after every mating cycle.

3. Mechanical design: the connector must balance a latching mechanism with durability.

4. Process compatibility: supporting wafer-level testing and passive alignment to reduce test and packaging costs.

3. SENKO's Technical Solutions

1. Optical design: expanded beam

   • Aligning fiber directly to a 9 µm core requires ultra-high precision of ±1 µm, which is nearly impossible to mass-produce in a detachable solution.

   • SENKO expands the beam to 40–45 µm, relaxing alignment tolerance to ±5–7 µm and improving fault tolerance.

2. Metallic mirror integration

   • Spherical or concave mirrors are embedded directly in metal to reshape the beam and reduce loss.

   • Supports high-density designs with 20–36 channels, with higher fiber-count versions under development.

3. Seat technology (elastic averaging seat)

   • SENKO's patented design builds the alignment mechanism into a "Seat" structure on both the connector and chip sides.

   • Features:

     • Repeatability: only 0.06–0.07 dB, better than MPO connectors.

     • Interchangeability: only 0.09 dB, supporting swaps between different modules and connectors.

   • Supports passive alignment, eliminating costly active alignment each time.

4. Use cases

   • Demonstrated an XPU module in collaboration with Marvell.

   • Joined the NVIDIA photonics ecosystem, supporting GPU networking architectures.

   • Developing a multi-chip module solution in which a single connector supports 300+ fibers.

4. Manufacturing and Test Advantages

• Wafer-level testing: Seat technology allows the receptacle to be installed at the wafer stage and verified through passive optical testing.

• Packaging compatibility: material selection matches the coefficient of thermal expansion (CTE match to silicon) and supports reflow processes.

• Lower cost: eliminating expensive per-unit active alignment sharply reduces test costs in high-volume production.

Conclusion

In its SEMICON 2025 talk, SENKO presented a complete solution to the fiber-to-chip connection challenge:

• 
  Expanded-beam technology relaxes alignment tolerance.

• 
  Metallic mirror structures increase optical path design freedom.

• 
  Seat technology delivers high repeatability, interchangeability and wafer-level testability.

These technologies not only make it easier for CPO to enter the volume production stage (2026–2027), but will also become a key foundation for large-scale deployment of optical modules in AI data centers.