Photonics Dictionary: F

A circuit that permits feedback in an electronic device.

A property of optical fiber that results from thermal stresses during manufacturing and is defined as the amount of curvature over any specified length of fiber.

The distance between the surface of a ferrule and the surface of a fiber end, provided that the ferrule extends above the fiber end. If the fiber end extends above the ferrule surface, the difference...

The process of grinding the concave surface of a single-vision spherical lens.

Describes devices that are not provided with a means of focusing.

1. The focal point. 2. To adjust the eyepiece or objective of a telescope so that the image is clearly seen by the observer. 3. To adjust the camera lens, plate, or film holder so that the image is...

1. A mechanism that permits the focusing of an optical system.2. A means of obtaining the sharpest image from a cathode-ray tube display by adjusting the size of the spot where it reaches the screen.

An incandescent or carbon arc lamp designed with a stable and compact arc or filament that permits it to be used as a light source to be focused by a lens system.

A single-particle scattering technique in which an incident laser beam is tightly focused by means of lenses to yield a focal spot in the scattering material with a diameter on the order of the...

One of the electrodes used to focus the electron beam of a cathode-ray tube. As the electrode's voltage is changed, its electrical field is changed, resulting in a change of the electron beam's spot...

A coil used to focus an electron beam by the generation of a magnetic field parallel to the beam.

A retroreflector that can focus a beam of light, with one planar reflective surface, one spherical and a third that is either planar or convex cylindrical.

A scale on an optical instrument that indicates the condition of focus. May indicate the distance to the object or diopter output, or from infinity focus.

A method of focusing an optical system by moving the front component (the lens closest to the subject) to change the distances between components. Also known as front-element focusing.

A multiple-beam interferometer, usually consisting of two flat plates, with high reflective ability. The plates are set parallel to one another by spacers so that lightwaves may bounce back and forth...

A means of determining a prism's index of refraction by placing the prism so that its emergent face is perpendicular to the incident beam. This arrangement permits the determination of the prism's...

A highly reflective mirror that is usually flat on one surface and curved on the other, and that has silver, gold or aluminum deposited on glass, providing about 99 percent reflection.

Measurement of the interval during which a photodetector's signal and output current drops from 90 to 10 percent.

The simultaneous collection of two or more signals at a single location. In a digital computer, it refers to the number of inputs that can be accommodated by a particular logic circuit.

The distribution of one signal to more than one location. In a digital computer, it refers to the number of outputs that can be fed by a particular logic circuit.

The object distance at which the eye is focused with the eye lens in a neutral or relaxed state.

A grating with very coarse rulings to match the long wavelengths in the far-infrared region. In the most efficient ruling method, grooves are cut in plane, solid aluminum alloy blanks.

The decrease of a component's efficiency, or a reduction in a material's light sensitivity, as the result of accumulated exposures to radiant energy.

The transfer of a part of a device's or circuit's output back to its input.

The placement of a device or an additional circuit into a feedback control system to improve its response in relation to a specific characteristic of the system.

A femtosecond laser is a type of laser that emits ultrashort pulses of light with durations on the order of femtoseconds, where one femtosecond is equal to 10-15 seconds. These lasers are capable of...

In microscopy, the measured distance between theoretical parallel lines that are drawn tangent to the particle profile and perpendicular to the ocular scale.

The mathematical expression of the probability of any given state of energy being occupied when a semiconductor is in thermal equilibrium.

Ferroelectric materials are a type of dielectric materials that exhibit spontaneous electric polarization, meaning they possess a permanent electric dipole moment even in the absence of an external...

A prism with curved faces that collimates, reflects and refracts incident light. Often used in the production of spectrographs.

A standard for fiber optic data transmission systems being developed by the American National Standards Institute (ANSI) and associated working groups that will make fiber optic components from...

A fiber laser is a type of laser in which the active gain medium is an optical fiber doped with rare-earth ions such as erbium, ytterbium, or neodymium. Fiber lasers generate coherent light through...

A fiber optic cable assembly refers to a complete unit consisting of optical fibers, connectors, protective jackets, and other components that are assembled together to facilitate the transmission of...

A plate consisting of fused optical fibers with both surfaces ground and polished, and having the entrance surface curved to match the image curvature of the input lens system. The plate transmits to...

A fiber optic gyroscope (FOG) is a type of gyroscope that uses the interference of light waves to detect changes in orientation or rotation. It operates based on the principle of the Sagnac effect,...

A fiber optic imaging bundle is a specialized optical device composed of multiple optical fibers bundled together. Each fiber optic strand within the bundle acts as a conduit for transmitting light....

A fiber optic preform is a cylindrical glass rod or tube used as the starting material for manufacturing optical fibers. It serves as the precursor from which optical fibers are drawn. The process of...

A device used for coding messages and having a fiber bundle that is aligned at both ends and scrambled in the middle, potted and cut. The resulting halves of the bundles serve as encoders or decoders...

A fiber optic spectrometer is a device used for measuring the spectral content of light. It utilizes optical fibers to transmit light from a source to a spectrometer unit, where the light is...

A fiber optic transceiver, often simply referred to as an "optical transceiver," is a device used in fiber optic communications to transmit and receive data over optical fibers. It integrates both a...

The use of thin flexible glass or plastic fibers as wave guides — or "light pipes" — to channel light from one location to another. Fiber optics is based off of the principle of total...

An optical recording technique that uses light source(s), a beamsplitting cube, light detector(s) and an optical fiber chronically implanted in animal brain to deliver excitation light to neurons...

A fiber-coupled LED (light-emitting diode) refers to an LED device that is optically coupled to an optical fiber for the purpose of efficient light transmission. In this configuration, the LED serves...

A fiber-coupled photoconductive antenna (FCPA) is a type of optoelectronic device that combines a photoconductive antenna with optical fibers for the purpose of generating or detecting terahertz...