NEC 2008 Annual Report Download - page 33

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Looking ahead, high-performance supercomputers
with petaflop*1-class processing speeds will be
required in around 2010. While internal CPU per-
formance is projected to improve in step with
continuous technological innovation in LSI device
technologies, realizing data transfer speeds
between LSIs with the capacity to supply data
volumes commensurate with CPU performance
has become a performance enhancement issue.
From the three years from fiscal 2006 to fiscal
2008, NEC participated in joint research with the
Tokyo Institute of Technology focused on the theme
of “R&D in Optical Interconnection Technology for
Ultra High-speed Computers.” This was part of a
research project of the Japanese Ministry of Educa-
tion, Culture, Sports, Science and Technology
(MEXT) called “R&D in Basic Next-generation Super-
computing Technology.” As a result, NEC has suc-
cessfully developed an optical interconnection
technology allowing ultra-high-speed and large
volume data transmission for next-generation super-
computers. By applying this technology to cutting-
edge LSIs in around 2010, NEC aims to achieve
ultra-high-speed data transfers in the order of 20
terabits*2 a second for every one LSI within a roughly
10 cm2 area on a printed circuit board. This will allow
a transmission volume that is approximately 1,000
times larger than that of current industry-standard
optical modules.
NEC has developed two main technologies. The
first is an optical module using vertical-cavity surface-
emitting lasers (VCSELs) that achieves the world’s
fastest signal transmission speeds. NEC developed
the world’s fastest VCSEL with an operating speed
of 25 Gbps*3, more than double conventional trans-
mission speeds, an opposing surface illuminated
photodetector, and an optical IC transceiver to oper-
ate the system’s optical elements. NEC also estab-
lished an integrated opto-electronic design technique
for incorporating all of these elements into an optical
fiber-based circuit-design model. This has enabled
multi-mode data transfers at 25 Gbps per signal over
circuits linked by 100 m of optical fiber, the world’s
longest optical interconnection. By doing so, NEC
has boosted data transmission speeds between LSIs
and between circuit boards, thereby eliminating a
major bottleneck to next-generation supercomputing
processing speeds. The second is ultra high-density
optical modules. NEC developed an ultra-small
optical module (12 signals), comprising flip-tip
mounted*4 optical elements on a ceramic substrate
5 mm wide and 7 mm long, and optical connectors
with internal optical wiring mounted on the optical
module circuit board. Through this advance, NEC
can mount ultra-small optical modules representing
approximately 1,000 signals within a 10 cm2 area
centered on LSIs mounted on printed circuit boards.
This allows the use of shorter electrical wiring
between LSIs and optical modules, enabling the
exchange of electrical signals with clean waveforms
between LSIs and optical modules.
Going forward, NEC will actively develop optical
interconnection technologies with the view to
broadly applying this technology to servers and
network equipment requiring large data capacities.
*1 1 petaflop: 1 quadrillion floating point calculations per second
*2 1 terabit: 1 trillion bits
*3 1 gigabit: 1 billion bits
*4 Technology for directly mounting optical elements onto
electrodes
10 mm
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