Editor's note: This article is by Dr. Will Green, Silicon Integrated Nanophotonics department manager, IBM Research
IBM’s research in brain-inspired computing
, quantum computing
, and silicon photonics is preparing to take computing in entirely new
directions. The neuromorphic chip is getting smarter, the quantum bits are being scaled out, and in the near future, my team’s CMOS Integrated Nano-Photonics Technology
will help ease data traffic jams in all sorts of
computing and communications systems – pushing cloud computing and Big Data
analytics to achieve their full potential.
For the first time, we have designed and tested a fully
integrated, wavelength-multiplexed silicon photonics chip capable of optically
transmitting and receiving information at data rates up to 25 Gb/s per channel.
This will soon make it possible to manufacture optical transceivers capable of
transmitting 100 gigabits of data per second.
Silicon photonics technology gives computational systems
the ability to use pulses of light to move data at high speeds over optical fibers, instead
of using conventional electrical signals over copper wires. Optical
interconnects, based on vertical-cavity surface-emitting laser (VCSEL)
technology and multi-mode fiber, are already being used in
systems today. But their transmission range is limited to a relatively short distance
of about 150 meters. Today, large data centers continue to scale in size to
support exponentially growing traffic from social media, video streaming, cloud
storage, sensor data, and much more. The longest optical links in such systems
can be more than a kilometer in length. As a result, new optical interconnect
solutions that can meet these requirements at low cost are needed to keep up
with future system growth.
How light boosts bandwidth
Our silicon photonics technology is designed to transmit
optical signals via single-mode optical fibers, which can support links many
tens of kilometers long. Moreover, we have built in the capability to use
multiple colors of light, all multiplexed to travel within the same optical
fiber, to boost the total data capacity carried. The recently demonstrated silicon
photonic chip can combine four wavelengths (all within the telecommunications
infrared spectrum), allowing us to transmit four times as much data per fiber.
The chip demonstrates transmission and reception of high-speed data at 25 Gb/s
over each of these four channels, so within a fully multiplexed design, we’re
able to provide 100 Gb/s aggregate bandwidth.
|A cassette carrying several hundred chips|
intended for 100 Gb/s transceivers,
diced from wafers fabricated with
IBM CMOS Integrated
In addition to the expanded range and bandwidth per fiber,
our new photonics technology holds several other advantages over what is
available today. Perhaps most importantly, the technology’s manufacturing makes use of
conventional silicon microelectronics foundry processes, meaning volume
production at low cost. In addition, the entire chip design flow, including
simulation, layout, and verification, is enabled by a hardware-verified process
design kit, using industry-standard tools. As a result, a high-speed
interconnect circuit designer does not require an in-depth knowledge of
photonics to build advanced chips with this technology. They can simply follow
the standard practices already in place in the CMOS industry.
This unified design environment is mirrored by our
integrated platform, which allows us to fabricate both the electronic and
photonic circuit components on a single silicon chip. Rather than breaking up
the electrical and optical functions, we integrated the optical components side by side
with sub-100nm CMOS electrical devices. This results in a smaller number of
components required to build a transceiver module, as well as a simplified testing
and assembly protocol, factors which further contribute to substantial cost
|Performance of the fully integrated, wavelength-multiplexed silicon photonics |
technology demonstrator chip. The eye diagrams illustrate four separate
transmitter channels (right) exchanging high-speed data with four receiver
channels (left), each running at a rate of 25 Gb/s.
While the primary applications for silicon photonics lie
within the data center market, driven by Big Data and cloud applications,
this technology is also poised to have a large impact within mobile computing.
There’s a need for low-cost optical transceivers to shuttle large volumes of data
between wireless cellular antennae and their base stations, often located many
kilometers away. As the data bandwidth available to mobile users increases
generation after generation, the number of individual cells required to support
the traffic does the same. Our technology can deliver faster data transfer in
higher volume and across larger areas, in order to support the inevitable
growth while controlling costs.
There has been significant discussion around the 50th
anniversary of Moore’s Law
and about whether it has reached its end. Silicon photonics fits into that "next switch"
conversation. On the processor side, there’s still a fairly consistent
trajectory in terms of CMOS technology scaling – down to 10nm, 7nm, and even smaller. The
role of our CMOS Integrated Nano-Photonics technology will be to reduce
communication bottlenecks inside of systems, and to allow expansion of their
capacity for processing huge volumes of data in real time.
Kilometer-scale data centers
are emerging. Big Data and the Internet of Things are connecting people and
information in ways that were unimaginable only a few years ago. IBM’s silico
n photonics technology will augment that growth on the
ground, into the Cloud, and beyond.
Labels: CMOS, photonics, silicon nanophotonics