Recently, TSMC announced that it will partner with Avicena, a startup based in Sunnyvale, California, to jointly advance microLED-based optical interconnect technology. Rather than a traditional laser path, this innovative solution replaces copper communication with micro-LEDs to meet the growing data transmission needs of AI clusters at a lower cost and with higher energy efficiency.
With the rapid development of AI technologies such as large language models, AI clusters are facing unprecedented challenges in terms of data volume, bandwidth, latency, and transmission speed. In order to meet these high-intensity communication needs, traditional copper connections will not be sustainable, and optical interconnect technology is imperative. Tsai Kit-rong, vice president of TSMC, said: "Now the industry is trying to bring optical interconnects as close to the motherboard as possible. "That's one of the reasons to work with Avicena.
Avicena has come up with a unique solution: hundreds of blue microLEDs work with imaging fibers to enable high-speed data transmission. Their modular LightBundle platform bypasses the complex and problematic laser systems found in traditional laser solutions, providing advantages in terms of reduced power consumption, cost, and improved reliability. Cai Jierong said frankly: "This method is indeed very different! But it's ideal for short-range communication scenarios, which is a testament to its unique value.”
Say goodbye to lasers
At present, optical communication in data centers usually transmits data at high speed through optical fibers ranging from tens to hundreds of meters, and relies on plug-in optical modules to achieve electro-optical conversion. However, these modules have the problems of high-power consumption, high cost, and low efficiency. To this end, the industry is actively promoting the development of "co-packaged optics" (CPO) technology, which places optical modules in close proximity to the chip package to achieve more efficient conversion. Although there is a commercial version of the CPO technology on the switch chip, the prototype on the GPU side is still in the experimental stage. Most current optical interconnect designs still rely on lasers and modulators to encode electrical signals into multi-wavelength optical signals.
However, lasers have always been a major challenge for optical interconnects. Whether it is manufacturing complexity, cost control, or long-term stability, lasers have become a key component of "stuck neck". In addition, when a single fiber carries multiple GPU-to-switch channels at the same time, a multi-wavelength scheme must be used for multiplexing, which in turn introduces additional computational overhead. In contrast, if each data channel corresponds to a separate physical fiber, the system design and processing are simpler and more efficient.
Avicena's technology is based on this philosophy. Their LightBundle technology connects each data channel separately with a multicore imaging fiber to transmit the light signal emitted by the blue microLEDs to the photoelectric detection array. In other words, the transmitter is like a small display, and the receiver is like a set of miniature cameras. "We're building an optical interconnect solution that doesn't require lasers," explains Pezeshki, CEO of Avicena.
With only 300 pixels and a transfer rate of 10 Gb/s per lane, a total bandwidth of 3 Tb/s can be achieved, covering a distance of 10 meters. And because camera and display technology is already scalable to megapixels, the solution has bandwidth density and energy efficiency that far exceeds that of copper.
Figure: TSMC bets on non-traditional optical technologies
The acceleration effect of mature industries
One of Avicena's biggest strengths is that it leverages the existing LED, camera and display value chain. "We are able to innovate combinatorically with mature industrial modules, which is far more efficient than developing lasers and new modulators from scratch." Pezeshki said. In contrast, although silicon photonics technology has been deeply cultivated for more than 30 years, its key devices such as ring resonators and frequency comb lasers are still in the process of slow maturity and are difficult to be implemented on a large scale.
That's why TSMC chose Avicena to provide critical photodetector array production support. "LEDs are a highly mature consumer electronics industry with low cost, low power consumption, and simple redundancy, making them ideal for in-rack interconnects within 10 meters," Cai said. "This natural advantage means that not only will there be good prospects for scale in the future, but also cost control will be more flexible.
Pezeshki added that the LightBundle prototype system has already achieved energy consumption of less than 1 picojoule per bit (pJ/bit), while mainstream silicon photonics solutions are still struggling to break through the 5 pJ/bit energy efficiency bottleneck. "We still have a lot of work to do, but the path to great performance with mature components is already gaining more and more supporters." He said.
This technology race about "next-generation AI data center optical interconnection" may have ushered in a real "dark horse".
