Light Pulses To Reduce Size of Supercomputers

In a paper published in the journal Optics Express, IBM researchers detailed a new computing technique that uses light pulses rather than electricity to transfer data. This could eventually provide laptops with the power of today’s fastest supercomputers which currently consist of thousands of individual processor "brains" connected by miles of copper wires.

The breakthrough -- in the form of a specially designed silicon Mach-Zehnder electro-optic modulator -- performs the function of converting electrical signals into pulses of light. In a computer, this would be used to transfer information between separate processes at a higher speed, and lower power consumption, than traditional wires.

The IBM modulator is 100 to 1,000 times smaller in size compared to previously demonstrated modulators of its kind, paving the way for many such devices and eventually complete optical routing networks to be integrated onto a single chip. This could significantly reduce cost, energy and heat while increasing communications bandwidth between the cores more than a hundred times over wired chips.


[Video Courtesy: IBM] IBM's optical modulator performs the function of converting a digital electrical signal carried on a wire, into a series of light pulses, carried on a silicon nanophotonic waveguide. First, an input laser beam (marked by red color) is delivered to the optical modulator. The optical modulator (black box with IBM logo) is basically a very fast “shutter” which controls whether the input laser is blocked or transmitted to the output waveguide. When a digital electrical pulse (a “1” bit marked by yellow) arrives from the left at the modulator, a short pulse of light is allowed to pass through at the optical output on the right. When there is no electrical pulse at the modulator (a “0” bit), the modulator blocks light from passing through at the optical output. In this way, the device “modulates” the intensity of the input laser beam, and the modulator converts a stream of digital bits (“1”s and “0”s) from electrical input pulses into pulses of light.

IBM's current Cell processor contains nine cores on a single chip, but the new device would allow the connection of literally hundreds or thousands of cores. In addition, the technique could transfer data at up to 100 times faster than electricity, to vastly improve the powers of computing systems. Also, while today’s supercomputers can use the equivalent energy required to power hundreds of homes, these future tiny supercomputers-on-a-chip would expend the energy of a light bulb.

It may be recalled that IBM's pioneering work to move the industry from aluminum to copper wiring, unveiled in 1997, had provided the industry an immediate 35% reduction in electron flow resistance and a 15% boost in chip performance. The current breakthrough may also lead a long way towards bringing the technology of supercomputer on our laptop.

Reference
“Ultra-compact, low RF power, 10 Gb/s silicon Mach-Zehnder modulator”
William M. J. Green, Michael J. Rooks, Lidija Sekaric, and Yurii A. Vlasov
Optics Express, v15, p.17106-17113 (2007) Abstract