Thursday, August 23, 2007

Silicon Photonics

Unlike electronicdata, optical signals can travel tens of kilometers without distortion or attenuation. One can also pack dozens of channels of high-speed data onto a single fiber,. Today, 40 separate signals, each running at 10 gigabits per second, can be squeezed onto a hair-thin fiber. Inside the PC, though, it’s copper all the way. Why? Because photonic components are expensive. Today’s devices are specialized components made from indium phosphide, lithium niobate, and other exotic materials that can’t be integrated onto silicon chips. That makes their assembly much more complex than the assembly of ordinary electronics, because the paths that the light travels must be painstakingly aligned to micrometer precision. In a sense, the photonics industry is where the electronics industry was a half century ago, before the breakthrough of the integrated circuit.

Billion bits per second

The only way for photonics to move into the mass market is to introduce integration, high-volume manufacturing, and low-cost assembly that is, to "siliconize" photonics. By that we mean integrating several different optical devices onto one silicon chip, rather than separately assembling each from exotic materials.

To understand how optical data might one day travel through silicon in our computers, it is needed to know how it travels over optical fiber today. First, a computer sends regular electrical data to an optical transmitter, where the signal is converted into pulses of light. The transmitter contains a laser and an electrical driver, which uses the source data to modulate the laser beam. Imprinted with the data, the beam travels through the glass fiber, encountering switches at various junctures that route the data to different destinations. At the destination, a photodetector reads and converts the data encoded in the photons back into electrical data.

Similar techniques could someday allow us to collapse the dozens of copper conductors that currently carry data between processors and memory chips into a single photonic link. To do that cheaply, though, we need to figure out how to render the optical components i.e the laser, the modulator, the photodetector, with the help of silicon

Silicon Photonics


Contributed By Richa

1 comment:

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