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switch n - переключатель; bit n - бит (информа­ции); trap л-ловушка; resolve v- (разрешать

Europe leads research in optical computing. Until now, the switches inside computers have been electronic. European scientists are planning to demonstrate the world's first optical computers. This demonstration will come 22 years after the theory behind optical computers was first predicted by researchers from the computer company IBM. However, there is still a large gap (раз­рыв) between what theoretical physicists believe can be done, and what electronic engineers know is possible.

*In theory, optical switches leave their electronical counterparts standing. It is like comparing the speed of light with the speed of electricity. *Optical switches are so fast and yet so small that an optical device of one square centimetre can resolve 10⁷ separate spots of light and each can be switched on and off at a speed of 30 nanoseconds.

This means that an optical device one square cen­timetre in area could, in theory at least, handle 3 "x 10¹⁴ bits per second. This rate is equivalent to everybody in the world having a telephone conversation at the same time.

The optical switch works on the principle of optical "bistability". Usually, when a beam of light is passed through a transparent material, the relationship between the intensities of light entering and the light leaving is linear. However, under certain circumstances a non-lin­ear relationship occurs. A small increase in the intensity of light entering the material leads to a much greater in­crease in the intensity of light leaving the material.

In optical switches the material is placed inside a resonant cavity (полость). In practice, this means that

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the edges of the material are highly polished and parallel to each other. With such materials some of the light entering becomes "trapped" inside as it bounces back and forth against each polished surface. In other words, it resonates. This changes the refractive index of the material, with the result that for a given intensity of light entering the switch there are two possible intensities of light leaving it.

*In other words, there is an equivalent to an "off" position and an "on" position because there are two sta­ble states and the material shows optical bistability. Up to now a switching speed of 10"¹³ seconds has been achieved, although the power needed to generate this is in the kilowatt range. A speed of one nanosecond (10~⁹) is possible in the milliwatt power range.