IBM Turns on -Light Switch' for Chips

Big Blue researchers have now developed a switch that will control the flow of data within chips that use light pulses instead of copper wires.

IBM researchers are taking the next significant step in developing microprocessors that use light beams instead of traditional copper wires to transmit data from one processing core to another.

In a paper published March 17 in the journal Nature Photonics, IBM engineers detail a new nanophotonic silicon broadband switch that will route optical pulse signals within a microprocessor from a transmitting core to a receiving core. These optical switches are extremely small and 2,000 of them could fit within one square millimeter, according to IBM.
The optical switch IBM is detailing is a critical part of its efforts to build chips that use light pulses instead of wires. In December, the company announced it had developed a silicon modulator that converts electronic signals into light beams. The optical switch then takes those light beams and, acting like a traffic cop, directs those beams from core to core.
If and when IBM fully develops these chips, the microprocessors will use less energy and heat than the conventional processors used today. It will also allow for increased bandwidth-it's possible the data will travel 100 times faster, while using 10 times less power-within the chip and allow engineers to place hundreds of processing cores on a single piece of silicon.
With conventional technology, companies such as Intel, Advanced Micro Devices, Sun Microsystems and others have all moved toward adding more cores and new technology onto each new generation of microprocessors. By using more conventional methods, Intel will begin offering eight-core x86 processors later this year.
IBM already offers nine processing cores with its Cell processor.
Now IBM researchers are hoping to accelerate the process of adding more processing cores on each by replacing traditional copper wires with light pulses, which allow the data to travel much greater distances. The use of light instead of electrical signals will also help reduce the amount of heat a chip dissipates.
In addition to being extremely small, IBM researchers have also developed technology that allows the optical switch to send large amounts of data through different wavelengths simultaneously.
Each of these wavelengths is capable of carrying data at 40 gigabits a second, which means it's possible that a chip could have an aggregate bandwidth of 1 terabit per second. This bandwidth is critical for sending large amounts of data across significant distances within the microprocessor.
This type of bandwidth is not capable within processors that use copper wiring, according to IBM.
The design will also help with chip parallelism that uses numerous cores with multiple instructional threads to increase performance. The optical design allows the chips to receive and transmit large amounts of data simultaneously, which would require large amounts of energy in a chip using copper wires.
The report on these optical switches, "High-throughput silicon nanophotonic wavelength-insensitive switch for on-chip optical networks," can be found in the April 2008 edition of the Nature Photonics journal.