Optical Carrier 12


(OC-12) A SONET rate of 12 * 51.84 = 622.08 megabits per second.

[Matches STS-12]?

Last updated: 1997-05-26

Optical Carrier 3


(OC-3) A SONET rate of 3 * 51.84 = 155.52 megabits per second, which matches STS-3.

Last updated: 1997-02-05

Optical Carrier 48


(OC-48) A SONET rate of 48 * 51.84 = 2488.32 megabits per second.

[Matches STS-48]?

Last updated: 1997-05-26

Optical Carrier n


(OC-n) A SONET rate of n times 51.84 megabits per second.

Last updated: 1997-02-05

Optical Character Recognition


(OCR, sometimes /oh'k*/) Recognition of printed or written characters by computer. Each page of text is converted to a digital using a scanner and OCR is then applied to this image to produce a text file. This involves complex image processing algorithms and rarely achieves 100% accuracy so manual proof reading is recommended.

Last updated: 1999-08-26

optical computing


(Or "Optical Signal Processing") Operating on data represented using electromagnetic radiation, e.g. visible light, instead of the electrical signals used in a conventional electronic digital computer.

Electronic digital computers are built from transistors. These form components that store data and logic gates that perform the low-level Boolean operations such as AND, OR and NOT that are the basis of all digital computation.

The optical equivalent requires material with a non-linear refractive index such that light beams can interact with each other to perform the same Boolean operations.

Though the photons that carry optical signals offer some theoretical advantages over the electrons that carry electronic signals, there are many practical problems that would have to be overcome before optical computing could compete in terms of cost, power and speed.

Last updated: 2015-08-21

optical diff


optical disc drive

optical disk drive

optical disk drive


(Or "optical disc drive", "optical storage") A generic term for any device that reads and/or writes optical media, i.e. compact discs, DVDs and/or Blu-ray discs or future media that uses light (from a small laser) to read data off a removable, rotating disk.

At least one such drive is commonly installed in most personal computers to allow them to play and/or record audio and video media and load and store data such as program installers.

The floppy disk has been replaced by optical media due to its vastly greater capacity, e.g. 50,000 megabytes for a dual-layer blu-ray disc compared with 1.5 megabytes for a floppy (over 30,000 times as much).

Last updated: 2014-04-27

optical drive

optical disk drive

optical fiber

optical fibre

optical fibre


(fibre optics, FO, US "fiber", light pipe) A plastic or glass (silicon dioxide) fibre no thicker than a human hair used to transmit information using infra-red or even visible light as the carrier (usually a laser). The light beam is an electromagnetic signal with a frequency in the range of 10^14 to 10^15 Hertz.

Optical fibre is less susceptible to external noise than other transmission media, and is cheaper to make than copper wire, but it is much more difficult to connect. Optical fibres are difficult to tamper with (to monitor or inject data in the middle of a connection), making them appropriate for secure communications. The light beams do not escape from the medium because the material used provides total internal reflection.

AT&T Bell Laboratories in the United States managed to send information at a rate of 420 megabits per second, over 161.5 km through an optical fibre cable. In Japan, 445.8 megabits per second was achieved over a shorter distance. At this rate, the entire text of the Encyclopedia Britannica could be transmitted in one second. Currently, AT&T is working on a world network to support high volume data transmission, international computer networking, electronic mail and voice communications (a single fibre can transmit 200 million telephone conversations simultaneously).

See also FDDI, Optical Carrier n, SONET.

Last updated: 1997-05-26

optical grep


Optical Mark Reader


(OMR) A special scanning device that can read carefully placed pencil marks on specially designed documents. OMR is frequenty used in forms, questionnaires, and answer-sheets.

Last updated: 1995-04-13

optical mouse


Any kind of mouse that uses visible light or infrared to detect changes in its position.

Last updated: 1999-07-21

Optical Signal Processor

optical computing

optical storage

optical disk drive

Optical Storage Technology Association


(OSTA) An industry consortium concerned with optical storage. OSTA wrote and maintains the UDF file system used on DVD video discs.

OSTA Home.

Last updated: 2003-07-12

Optical Time Domain Reflectometer


A device used to perform Optical Time Domain Reflectometry.

Last updated: 1995-02-01

Optical Time Domain Reflectometry

Measurement of the elapsed time and intensity of light reflected on optical fibre using an optical time domain reflectometer. The reflectometer can compute the distance to problems on the fibre such as attenuation and breaks, making it a useful tool in optical network trouble-shooting.

Last updated: 1995-02-01

Nearby terms:

OPS83Optical Carrier 12Optical Carrier 3Optical Carrier 48

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