Avicena touts LED-based LightBundle optical interconnects for chip-to-chip communication

June 17, 2021
The company’s LightBundle leverages microLED light sources and multicore fibers to create highly parallel interconnects that Avicena sources say can enable chip-to-chip communications at distances up to 10 m.

Mountain View, CA, based startup Avicena Inc. has announced an optical interconnect based on technology from the imagery and display worlds. The company’s LightBundleTM leverages microLED light sources and multicore fibers to create highly parallel interconnects that Avicena sources say can enable chip-to-chip communications at distances up to 10 m.

At the heart of the LightBundle is the company’s Cavity-Reinforced Optical Micro-Emitters (CROMEs), based on GaN microLEDs, according to Chris Pfistner, who works in marketing and business development with Avicena. Such visible light emitters are commonly used in the display arena, but typically can transmit less than 1 Gbps of information. Avicena has developed a way to boost that output to approximately 10 Gbps, Pfistner says. The blue CROMEs are bonded to CMOS in a highly parallel array alongside arrays of silicon photodetectors grown directly in CMOS. The technology is capable of producing 10 Tbps per square millimeter at a power efficiency of less than 0.5 pJ/bit, Pfistner asserts. The CROME emitters can operate at ASIC temperatures, meaning they can serve reliably as internal laser sources for co-packaged optics without cooling.

The CROMEs and PDs at each end of the connection will be linked by passively aligned multicore fiber, a technology common in imagery applications such as endoscopy. Pfistner allows that the fiber technology will have to be optimized for Avicena’s target applications of high-performance computing, cloud computing, and data center networking, but expects the multicore fiber, in a diameter of about 1 mm, to support hundreds of channels for Avicena initially with a runway to future channel counts in the thousands.

In a post-deadline paper delivered this past Friday at OFC 2021 (F3A.1, “Wide and parallel LED-based optical links using multi-core fiber for chip-to-chip communications”), Avicena reported on a demonstration of an array of more than 200 devices at a 30-mm pitch coupled simultaneously through a 0.5-mm imaging fiber. As high-speed drivers were not yet ready in an array format, the CROME arrays were driven at low speeds – 2 Gbps, according to Pfistner. However, the engineers conducting the demonstration also were able to package the CROME with an external driver and showed what the paper authors termed “excellent link characteristics” up to 10 Gbps.

With the ability to support 10-m reach, the technology could be used for chassis-to-chassis applications. The electrical interface between the CROME and the host chip will need to be determined. However, Pfistner notes this issue is still being worked out for co-packaged optics in general.

The company likely will work with partners, certainly to produce the LightBundle elements and possibly to speed development, Pfistner indicated. Avicena expects to introduce its first product in the second half of 2022.

Avicena is led by CEO Bardia Pezeshki and CTO Rob Kalman, both of whom cofounded the company after working together most recently at Kaiam. The company’s website lists Samsung Catalyst Fund and Clear Ventures as investors.

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