As we have seen with the IC industry, the value of integration comes not
from combining a handful of transistors, but by putting millions of transistors
together and scaling them to faster and faster speeds over time.
mate with a hand-pluggable fiber connector containing a molded
plastic lens assembly to direct light into the optical fiber.
The output power from the four hybrid silicon lasers, measured
at the output of the integrated transmitter die, ranges from 2 to
9 mW. The transmitter has a rise/fall time of 41 to 44 ps, an
extinction ratio ranging from 4. 4 to 6. 3 dB and a total jitter of
23 to 34 ps. We conducted bit error rate (BER) measurements
at the data rate up to 12. 5 Gbps per channel. These results are
promising: With a data rate of 10 Gbps, we’ve been able to
run the link for more than a day, transferring over 1 petabit of
data, without errors, suggesting a BER of less than 3 3 10-15.
We then increased the modulation speed and showed that individual channels could operate at up to 12. 5 Gbps per channel
with BER of less that 10-12. This puts the aggregate link speed
at 50 Gbps overall.
Looking to the future
As we have seen with the IC industry, the value of integration
comes not from combining a handful of transistors, but by
putting millions of transistors together and scaling them to
faster and faster speeds over time. Most fiber-optic technologies
sold today are composed of several separate, discrete, optical
components that are often hand-assembled to form an optical
link. The successful multichannel integration demonstrated by
this 50 Gbps link suggests that silicon photonics could further
increase the number of parallel channels on each chip and scale
to much higher data rates.
The day we saw the link reach 50 Gbps in the lab was both
memorable and incredibly rewarding for the research team.
However, at the same time it is only a stepping stone to much
higher speeds. This integration platform provides us two vectors to scale performance. The first is to “scale up” the individual device speeds in the link. We have shown that we can
run individual modulators and detectors to 40 Gbps, and we
believe we can reach these speeds for the integrated link over
time and perhaps reach even higher speeds. Simply doing so
would enable us to reach 160 Gbps aggregate bandwidth with
the same four channels.
We can also “scale out” by integrating more optical channels
per chip, moving from 4 to 8 or 16 channels, for example. By
combining both vectors, we easily envision delivering data rates
of hundreds of gigabits per second, and ultimately more than a
terabit per second from a single integrated silicon photonic chip.
ONLINE EX TRA: Visit www.osa-opn.org for a video
demonstration of Intel’s 50 G silicon photonics link.
Paths to scaling the link data rates towards terascale performance [ ] Scale up 8, 16, 32 channels… Modulate at 25, 40, 100 Gbps…
Courtesy of Intel Corp.
This 50 Gbps link represents a huge step forward in our
research, but there is more to be done as we take this technology from research to commercialization. On the silicon
front, we will continue to optimize device performance. For
the transmitter, we will push to drive modulators to operate
at lower operating voltages to reduce power consumption as
well as to maintain compatibility with ever-decreasing CMOS
operating voltages (such as for 45-nm and 32-nm processes).
We will also continue to improve the efficiency of the hybrid
silicon laser and work to reduce the threshold voltage, again to
minimize overall power consumption.
Looking to the coming century, every manufacturer of a
connected device in the future should start thinking about how
high-bandwidth, low-cost optical communications will benefit
the products and services they deliver. Integrated silicon photonics is the start of bringing optical communications to anyone,
anywhere around the world using optical communications. We
are just at the beginning. t
Sean Koehl, Ansheng Liu and Mario Paniccia ( mario.paniccia@
intel.com) are with Intel Labs in Santa Clara, Calif., U.S.A. Member
[ References and Resources ]
>> Cisco Visual Networking Index: www.cisco.com/en/US/solutions/
>> L. Liao et al. “ 40 Gbit/s silicon optical modulator for high speed
applications,” Electron. Lett. 43( 22), 2007.
>> T. Yin et al. “ 31 GHz Ge n-i-p waveguide photodetectors on silicon-on-insulator substrate,” Opt. Express 17, 13965-71 (2007).
>> A. W. Fang et al. “Single-wavelength silicon evanescent lasers,”
IEEE J. Sel. Quantum. Electron. 15( 3), May/June 2009.
>> The Economist, “Data, data everywhere,” February 2010.