How AI Workloads Are Driving the Rise of All‑Optical Switches

Background

AI training workloads are increasing the demand for high‑bandwidth, low‑latency data‑center networking. Traditional OEO (optical‑to‑electrical‑to‑optical) packet circuit switches rely on an AISC chip to perform packet forwarding, requiring optical‑electrical conversion at both ends.

From OEO to OOO: Fully Optical Switching for AI

HUBER+SUHNER explains that OOO (all‑optical) switches do not perform any electrical processing; they forward signals purely in the optical domain, eliminating the conversion step. This reduces latency and power consumption, making OOO switches attractive for AI compute clusters.

Lightmatter’s Passage Technology

In July 2024, NVIDIA executive Simona Jankowski joined Lightmatter as CFO. Lightmatter’s Passage product uses waveguides instead of fibers to interconnect heterogeneous compute cores (CPU, GPU, FPGA, DRAM, ASIC) within a single 3‑D package, delivering extremely high parallel interconnect bandwidth.

Fully integrated chip‑scale interconnect with direct fiber connections.

Flexible architecture supporting various configurations (e.g., 1×1, 2×2, 2×4).

High‑bandwidth I/O that links multiple high‑performance components in a single 3‑D package.

Integration of photonics and control electronics for high performance density.

Built‑in reconfigurable optical circuit switch (OCS) and control mechanisms for redundancy and reliability.

WDM modulation enables multi‑λ bidirectional transmission on a single waveguide or fiber, increasing bandwidth.

Google’s Large‑Scale OCS Deployment

Google’s data‑center network strategy combines SDN, Clos topology, and commercial switching chips. It was an early adopter of OCS (optical circuit switch) technology, integrating MEMS‑based optical switches into its Jupiter architecture to replace the SP layer’s EPS, thereby reducing optical‑electrical conversion.

Google’s OCS design features 136 input and output channels, each using fiber collimator arrays and micro‑lens arrays. Two 2‑D MEMS arrays, each with 136 planar mirrors, steer light precisely, while two monitoring channels operate at 850 nm.

To manage channel count, Google pairs OCS with FR optical modules, employing Z‑block or AWG components and a ring resonator for bidirectional transmission, simplifying optical path control.

Key Takeaways

All‑optical switches, whether OEO‑enhanced or fully OOO, are emerging as critical infrastructure for AI‑driven data centers. Lightmatter’s integrated photonic approach and Google’s MEMS‑based OCS deployments illustrate two complementary paths toward higher bandwidth, lower latency, and more flexible networking.