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PsiQuantum turns its photonics know-how into an optical switch for supercharging AI data center GPU networks — 8x8 lab prototype loses less light than rivals, with plans to develop larger devices
Google’s mirror switches have 136 ports; PsiQuantum’s chip has eight, with larger devices in development.
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PsiQuantum, a quantum computing company, announced in a release earlier this week that it has turned its low-loss silicon photonics into an optical switch for use in AI data centers. Every optical switch typically comes with loss of light: the more light a switch receives, the less reaches the other side, with the amount of light lost measured in decibels. Typical data center optics can tolerate half the light (3 dB) being lost. PsiQuantum's switch debuted with a demo that typically loses only 1.2 dB of signal, or about a quarter of the light in lab tests, and the all-optical switch can achieve it without an amplifier. The prototype is, however, comparatively small, with eight inputs and outputs (8x8) against competitors’ 32 to 300, but the company says larger devices are in development.
The optical circuit switch (OCS) passes light straight through, from fiber to fiber, without converting it to or from electrical signals. Regular data center switches make that conversion at every hop, which takes power and adds latency. An OCS, instead, uses a fixed light path that it maintains until a change is ordered. Its main penalty comes down to how much light is lost when passing through the switch. PsiQuantum’s switch, which uses circuits etched on a silicon chip with no moving parts, unlike Google’s and Lumentum’s tiny mirrors, or microelectromechanical systems (MEMS), would be used alongside regular packet switches.
Skipping those conversions matters more as AI clusters grow, because moving data between GPUs is quickly becoming a bottleneck. Optics are a high-bandwidth improvement over copper, which has limitations in reach, although a shortage of lasers is a problem for the alternative. Improving communication bandwidth and distance is the goal, so that different racks of GPUs can talk at speed and act as one.
Switches similar to PsiQuantum’s made by Salience Labs and iPronics use built-in amplification and, at least in the former case, are also rated at under 2 dB, or under 37% of the light lost. Google’s mirror-based switch, Palomar, can also typically stay under 2 dB and has 136 ports. Salience’s switch sits at 32 and Lumentum’s at 300, which leaves the eight-port prototype a ways behind on how many fibers it can handle.
1.2 dB (about 24% of the light lost), typical in the company’s lab tests
Silicon photonics chip, no amplification, no moving parts
Typically under 2 dB (under 37% lost) across all port pairings; 2 dB worst case
Close to 1.5 dB (about 29% lost), typical at start of life, Lumentum’s switching GM told Gazettabyte