Optical Computing - Misconceptions, Challenges and Prospects

Misconceptions, Challenges and Prospects

A claimed advantage of optics is that it can reduce power consumption, but an optical communication system will typically use more power over short distances than an electronic one. This is because the shot noise of an optical communication channel is greater than the thermal noise of an electrical channel which, from information theory, means that more signal power is required to achieve the same data capacity. However, over longer distances and at greater data rates, the loss in electrical lines is sufficiently large that optical communications will comparatively use a lower amount of power. As communication data rates rise, this distance becomes longer and so the prospect of using optics in computing systems becomes more practical.

A significant challenge to optical computing is that computation is a nonlinear process in which multiple signals must interact to perform computations. Light, which is an electromagnetic wave, can only interact with another electromagnetic wave in the presence of electrons in a material, and the strength of this interaction is much weaker for electromagnetic waves such as light than for the electronic signals in a conventional computer. This results in the processing elements for an optical computer requiring more power and larger dimensions than those for a conventional electronic computer using transistors.