15.4.2 Optical computing
Optical computing, also known as photonic computing, focuses on constructing computing systems that use light (i.e., photons) instead of electricity (i.e., electrons) to carry out data transport and logic operations.
Our present computing and communications infrastructure is a hybrid of electronic and photonic components. Most high-speed, long-distance data and voice traffic is conducted over fiber optic cables, which transmit their data as pulses of light. Many high-speed local area networks use fiber optics as well – for example to move data between buildings on a college campus. Data manipulation, as opposed to data transport however, happens in the electronic domain. Thus, data must be continuously translated between the optical and electronic domains as it is shuffled from network to network. Unfortunately, electronics operate at speeds that are orders of magnitude slower than optics.
An analogy of the state of today’s current data and communications networks that I find useful is to imagine the Interstate highway system which enables rapid and efficient vehicle transport between major cities – these Interstate highways are like the long distance fiber optic links in our networks. Now, imagine that instead of having freeway interchanges with their arching on and off ramps in major cities where Interstates meet, all our cities had only dirt paths for roads. If you were traveling across country by car travel time between cities wouldn’t be a big deal, but passing through intermediate cities on your way to your final destination would be excruciating slow and painful. These dirt paths inside the cities are like the routers and switches, electronic devices, used to move data from one fiber optic cable to another
There is a lot of work going on in academia and corporate research labs to construct the basic building blocks of optical computers, such as photonic transistors. Optical computing promises many advantages over electronic computing, such as much faster speeds, smaller devices, and less power consumption. However, the obstacles to fully realizing optical computing are formidable.
Though all optical computing is probably several decades away – if it ever proves practical at all – hybrid electronic / photonic devices are a near term likelihood. IBM and Intel (among others) are working on silicon photonics, a technology that integrates both electronic and optical components onto a single silicon chip which can be manufactured using existing semi-conductor fabrication techniques. The underlying concept is that the individual components of a computer system, (e.g., the CPU and main memory) could exchange data between themselves optically rather than electronically. While the ‘computing’ would still be conducted in the electronic domain, data transport functions within the computer would move to the optical domain. The result would be systems that operate much faster than conventional electronics while using less power. It is anticipated that these hybrid systems will initially be used for data transport between individual integrated circuit chips, migrating over time to moving data between different regions of the same chip. In December 2012, IBM announced the first commercially viable silicon photonic chip.[9] Expect to see this technology roll out in the 2015 – 2020 timeframe, first in supercomputers and later in consumer devices.
Footnotes
[9] http://www-03.ibm.com/press/us/en/pressrelease/39641.wss