Key Findings
Lightmatter is developing a scalable optical interconnect architecture to overcome the I/O limitations of traditional electrical connections in large-scale AI clusters. The company’s strategy focuses on increasing fiber bandwidth density, enhancing chip-to-optical connection density via photonic interposers, and simplifying system maintenance through detachable interfaces and integrated lasers.
Technical Details
To optimize fiber utilization, Lightmatter employs Dense Wavelength Division Multiplexing (DWDM) and Bidirectional transmission (BiDi). Two platforms demonstrate these capabilities:
- Passage EVK50: Uses 16 wavelengths at 56Gbps NRZ per wavelength, achieving 400Gbps bidirectional transmission per fiber over 1km.
- Passage EVK100: Uses 16 wavelengths at 112Gbps PAM4 per wavelength, achieving 1.6Tbps unidirectional bandwidth over 1km.
Both platforms report energy consumption below 3pJ/bit. To address packaging I/O constraints, the Passage M1000 photonic interposer utilizes a 4000 square millimeter area with 1024 channels of 56Gbps NRZ signals and 8 wavelengths to reach a total bandwidth of 114Tbps, incorporating approximately 140,000 through-silicon vias (TSV).
Infrastructure and Integration
For system maintenance, Lightmatter introduced two detachable fiber interfaces with insertion loss below 1.5dB: eClick (edge-coupled with lens-based expanded beam fiber arrays) and vClick (vertical-coupled, compatible with molding and polishing processes). Additionally, the Guide Very Large Scale Photonics (VLSP) platform uses 300mm CMOS SOI wafer processes to integrate over 128 lasers per chip, with plans to expand to over 64 wavelengths.
Significance and Outlook
The Passage L20 optical engine is planned for Q1 2027, featuring 32 ports at 200Gbps PAM4 per channel, providing 6.4Tbps unidirectional (12.8Tbps bidirectional) bandwidth with a maximum TDP of 30W. While Lightmatter has developed a 204.8Tbps switch production verification platform with Flex and a 102.4Tbps XPU tray prototype, the company notes that large-scale deployment depends on the coordination of foundries, packaging providers, and fiber suppliers.
Source: https://news.qq.com/rain/a/20261025A046F800
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