Integrated photonics to illuminate the data center | by Intel Author | Intel Tech | May 2021
Author: Jeff W. Hockert, Senior Marketing Manager at Intel
As electrical interconnects face performance barriers and data centers face an electrical wall, Intel is advancing its vision of integrated photonics. By transmitting data optically, at lower latencies, higher bandwidth, and much lower power than is possible with electrical connections, Intel believes that integrated photonics will fundamentally change data center architectures.
Intel Silicon Photonics vision started in 2004 with the objective of bringing together optical and electronic functions in a single chip. Much progress has been made since then. For example, there are now over 4 million Intel 100G optical transceivers used for rack-to-rack connectivity – connecting row switches and director class switches across all data centers.
Today, fiber optic interconnects dominate long distance interconnections, while electricity dominates short distances. Our goal is to advance optical performance and replace electrical by bringing optical I / O directly into servers for board-to-board and package-to-package connectivity.
And the need is there: the current I / O performance of electrical interconnects faces practical performance limits. Equally important, data centers face issues of power consumption. Computing bandwidth demand doubles approximately every two years deux. However, the scaling of electrical performance does not keep pace with the demand for bandwidth. In addition, the energy efficiency of electrical I / O has recently slowed, leading to an approach to the electrical wall. Specifically, the I / O power tends to be greater than the total available socket power, leaving nothing for the computation.
In traditional server systems, scaling the electrical interconnect requires higher data rates and the addition of more I / O pins, which increases the size of the package to meet the demand. bandwidth request. However, this does not solve the electrical wall. Without fundamental advances, these two trends will not change over time. Optical I / O has the potential to be more efficient than electrical I / O while simultaneously providing> 1000 times the range². By tightly integrating the optics into a server package using silicon photonics, we can achieve three benefits in a small footprint: (1) lower power (2) higher bandwidth, and (3) reduced pin count .
We call this research vision integrated photonics and believe it will fundamentally change the network architectures of our data centers. This will allow data to move much more efficiently through the data center, both with lower power and lower latency. Our research targets are 1TB / s per fiber at @ 1pJ / b with a range of up to 1 km. By reducing optical I / O power below electrical I / O and miniaturizing the footprint of our silicon photonics devices to reduce costs, we are confident that we can address the I / O power wall. S approaching.
Let’s explore and see what technologies are needed to realize Intel’s vision of connecting data centers to light. AT Intel Labs Day 2020, held on December 3, Intel showcased photonic integrated circuits with fully integrated photonic functions including laser, amplifier, and ring modulators / detectors. We have shown breakthroughs in (1) micro-ring modulators, (2) an all-silicon photodetector, (3) laser-integrated optical amplifiers, and (4) integration of CMOS circuits.
We have developed micro-ring modulators a thousand times smaller than conventional silicon modulators. The micro-rings serve as a light modulator and silicon photodetector. Until now, the industry believed that silicon had virtually no ability to detect light in the 1.3-1.6 µm wavelength range, which was considered a fundamental limitation of photonic technology. silicon. This turned out to be wrong. On the receiver side, we have worked on all silicon ring photodetectors that combine wavelength selection and photodetection functions in a single device. Earlier this year, we released a light detection capability with an all-silicon photodetector and demonstrated this photodetector operating at a data rate of 112 Gb / s.
These ring photodetectors can be assembled with CMOS transimpedance amplifiers to construct low cost optical receivers. A major advantage of this approach is the reduction in processing and material costs.
We have integrated multi-wavelength lasers. We have shown a 4 wavelength laser that uses a single cavity, making it a more compact laser with uniform channel spacing. Another must-have technology is solid-state optical amplifiers. It is difficult to generate all the required light power from a laser. Fortunately, Intel optical amplifiers can be more energy efficient and it is important to note that they are made from the same material that is used for the integrated laser. Without the integrated laser, these amplifiers are not possible.
Finally, the co-integration of CMOS circuits and silicon photonics brings together all these technologies. Earlier this year, we described our ability to 3D stack CMOS electronic IC with our photonic IC using copper pillars. The CMOS electronic IC includes interface circuits for transmitting, receiving and thermally controlling the ring modulator to follow temperature variations.
By stacking the two integrated circuits directly on top of each other, we demonstrated the real potential of integrating micro-rings and CMOS circuits. Die-to-die integration results in a 3D integrated 100G silicon photon emitter capable of signaling at 112 Gbps.
Thanks to the excellent package integration technology developed by the Intel packaging group, we have the ability to integrate the most advanced CMOS technology and silicon photonics to provide our customers with products with high performance. unparalleled interconnection. Intel is unique in its ability to deliver integrated multi-wavelength lasers, solid-state optical amplifiers, all-silicon photodetectors, and micro-ring modulators on a single silicon technology platform, as well as the technology to integrate them tightly with silicon CMOS.
Integrating photonics into a server package is not a new idea. The main difference is that we now have all the technologies required on a single silicon photonics platform to make this vision a reality. With the size of our ring micro-modulators reduced to a few microns, we can integrate hundreds of optical I / Os in a small footprint. We believe that these types of optical links demonstrated at Intel Labs Day 2020 can be scaled to allow bandwidths of 10 to 100 terabits per second, and will increase optical I / O volumes from millions today to billions of units, thereby reducing manufacturing costs.