IBM Preps Optics to Replace Copper Interconnects
R. Colin Johnson | Date: 03-11-10 | Comments: 2
- Recently perfected optical interconnection technologies will obsolete copper traces for routing electronic signals around on printed circuit boards (PCBs) and even between cores inside microchips, according to IBM, which plans to commercialize on-chip optics over the next few years.
Optical fibers already carry the fastest communications
signals over the Internet and between servers and supercomputers at
high-performance data centers. By encoding electronic communications in the
language of light, the higher frequencies and wider bandwidth of optical
signals not only increases performance, but obsoletes heavy, bulky copper-based
interconnects in favor of small, lightweight optical fibers.
Future silicon CMOS
multicore microprocessor chips will use optical nanophotonics on its top layer
to interconnect memory and processor cores.
Unfortunately, all the optical interconnection technologies
today rely on expensive, discrete indium- and gallium arsenide-based
transceivers that cannot be integrated onto the same silicon-based chips as
processor cores. Consequently, optical fiber interconnects are only used
between computer systems today. In the future, however, IBM Research (Yorktown
Heights, N.Y.) and many other semiconductor development organizations worldwide
are pursuing silicon-based optical communications technologies that can be
integrated directly onto modern multicore processors.
Over the last decade, IBM in particular has begun announcing
breakthrough optical devices that can be integrated on standard silicon
multicore processor chips using complementary metal oxide semiconductors
(CMOS). But to enable optical communications between and among multicore
processors required developing a whole ecosystem of silicon-based optical
devices that IBM dubs its nanophotonic
toolkit.
Each year, IBM announces a few more elements in its nanophotonic
toolkit, including on-chip silicon-laser resonators, modulators, waveguides
and switches. Plus, it has demonstrated a complete chip-to-chip optical bus.
Now IBM claims it has crafted the final tool in its nanophotonics
kit -- a tiny germanium optical receiver called an avalanche photodetector -- that
will enable it to realize the dream of integrated CMOS optical interconnects.
The new 40G bps photodetector can be integrated on the edge of
processors to receive optical signals sent between chips instead of using
copper traces on printed circuit boards. And eventually, it will be integrated
on the top layer of the microprocessor itself to facilitate lightning-fast
communications between cores on the same chip, thus eliminating the need for
copper wires inside and outside future electronic devices.
Optical signals are not only faster, but can be encoded onto
different colors of light for multiplexed communications that are light-years
ahead of even the highest speeds attainable with copper wires. And for portable
devices, on-chip and between-chip optical interconnects promise to cut both the
power consumed -- thereby increasing battery life -- as well as the weight of
electronics. By eliminating the copper traces on printed circuit boards and the
copper wires inside the chips themselves, a major reduction can be made in the
weight of mobile devices today.
