61,984 articles
Opportunity charging
Opportunity charging is recharging battery-electric vehicles with short, high-power top-ups during dwell times already built into their schedules, at stops or termini, letting buses and trucks use smaller batteries.
Opposed-piston engine
An opposed-piston engine is an internal combustion engine in which two pistons share each cylinder, moving in opposite directions with the combustion chamber between them and no cylinder head.
Opposition-based learning
Opposition-based learning is a machine intelligence technique that pairs each candidate solution with its opposite point in the search space, keeping the fitter to speed convergence.
Oppositions
Oppositions was an American architectural journal published in New York by the Institute for Architecture and Urban Studies from 1973 to 1984, in 26 issues.
OPR-1000
The OPR-1000, originally called the Korean Standard Nuclear Power Plant (KSNP), is a South Korean 1,000 MWe two-loop pressurized water reactor developed from 1984 to 1999.
OPS-SAT
OPS-SAT was a 3U CubeSat of the European Space Agency launched in December 2019 as an in-orbit laboratory for testing mission control techniques, ending with atmospheric reentry in May 2024.
OPT (Meta model family)
OPT (Open Pre-trained Transformer) is a family of language models released by Meta AI in May 2022, with sizes from 125 million to 175 billion parameters, roughly matching GPT-3.
OPT-175B
OPT-175B is a 175-billion-parameter language model built by Meta AI like GPT-3 and released to researchers in May 2022 with training code and a complete training logbook.
Opteron
Opteron, or AMD Opteron, is a family of x86 server processors from AMD, introduced in 2003 as the first 64-bit processor compatible with the x86 architecture.
Optical add-drop multiplexer
An optical add-drop multiplexer (OADM) is a wavelength-selective device in WDM fiber systems that drops and adds wavelength channels at a site while other wavelengths pass through untouched.
Optical amplifier
An optical amplifier, also called a laser amplifier, is a device that boosts light signals directly without converting them to electricity, enabling long-haul fiber-optic transmission and dense wavelength-division multiplexing.
Optical attenuator
An optical attenuator is a passive device that reduces the power of an optical signal by a specified amount in decibels, existing as fixed or adjustable variable types.
Optical brightener
Optical brighteners, also called fluorescent whitening agents, are compounds that absorb ultraviolet light and re-emit it as blue fluorescence, making textiles, paper, and plastics look whiter.
Optical buffering
Optical buffering is the temporary storage of optical packets as light, without electrical conversion, using fiber delay lines that add fixed delays, since optical switches lack random-access memory.
Optical burst switching
Optical burst switching is a switching technique for optical networks in which edge nodes aggregate packets into bursts that intermediate nodes switch entirely in the optical domain, proposed in 1999.
Optical bypass
Optical bypass is a fiber network design principle in which transit traffic at an intermediate node is forwarded directly between fibers in the optical domain, avoiding costly electronic processing.
Optical channel monitoring
Optical channel monitoring measures the physical parameters of individual wavelength channels in WDM systems, such as power, wavelength, and OSNR, and impairments like chromatic dispersion.
Optical character recognition
Optical character recognition (OCR), also known as an optical character reader, is a technology that converts images of text, such as scans and image-only PDFs, into searchable, editable machine-readable text.
Optical circuit switch
An optical circuit switch (OCS) is a device that steers whole light paths between fiber ports with movable mirrors, without converting signals to electrical form or inspecting packets.
Optical circulator
An optical circulator is a non-reciprocal device with three or four ports that routes entering light to the next port in fixed cyclic order, used in full-duplex fiber communication.
Optical code-division multiple access
Optical code-division multiple access (OCDMA) is a multiplexing technique in which each user's data on a shared optical channel is encoded with a unique optical code, letting receivers separate users by correlation.
Optical critical dimension
Optical critical dimension metrology, most often called scatterometry, is a model-based optical technique that measures dimensions and shapes of nanostructures on semiconductor wafers for in-line chip manufacturing process control.
Optical current transformer
An optical current transformer is a power-system device that measures current via the Faraday effect on polarized light, offering no core saturation and a wide dynamic range.
Optical Devices
Optical devices are items or components used to detect, manipulate, or analyze light, such as lenses, mirrors, prisms, and optical fibers, underpinning fields from telecommunications to medicine.
Optical disc
An optical disc is a flat, circular storage medium read and written by a focused laser, running from the CD (1982) through DVD (1995) to Blu-ray (2003).
Optical disc drive
An optical disc drive (ODD), also called an optical drive, is a device that uses laser light to read and write CDs, DVDs, and Blu-ray Discs, and has largely disappeared from new laptops.
Optical frequency-domain reflectometry
Optical frequency-domain reflectometry (OFDR) sweeps a tunable laser along optical fiber to map reflections, also measuring distributed temperature and strain with resolutions down to tens of micrometers.
Optical frequency-shift keying
Optical frequency-shift keying, or optical FSK, is a modulation format that encodes data by shifting an optical carrier between discrete frequencies, attractive because lasers can be modulated directly by drive current.
Optical ground station
An optical ground station is a ground-based facility with a telescope, laser transmitters, and sensitive receivers that communicates with spacecraft using free-space laser links instead of radio frequencies.
Optical ground wire
Optical ground wire (OPGW), also called optical fiber composite overhead ground wire, is a metallic cable at the top of transmission towers that shields against lightning while carrying optical fibers, in regular use since the mid-1980s.