Fiber Optic :: Glossary :: F

Fall time - The time required for the trailing edge of a pulse to fall from 90% to 10% of its amplitude. The time required for a component to produce such a result. Turn off time. Sometimes measured between the 80% and 20% points.

Fan Out cable - Same as a Break Out cable. This is a multiple fiber optic cables constructed in the tight buffered design. It is designed for ease of connectorization and rugged applications for intra-building and inter-building requirements.

FC - A connector type. It is utilized for single-mode fiber optic cable. It offers extremely precise positioning of the single-mode fiber optic cable with respect to the emitter and detector. It features a position locatable notch and a threaded receptacle. Once installed, the position is maintained with absolute accuracy.

FC/PC - A connector type. It is utilized for single mode cable. It offers extremely precise positioning of the single mode cable with respect to the emitter and detector. It features a position locatable notch and a threaded receptacle. Once installed the position is maintained with absolute accuracy.

FDD I - Fiber Distributed Data Interface. A very high-speed local area networking architecture based upon fiber optic cable as the transmission medium. Many FDDI features were incorporated into Fast Ethernet-100Base-T. FDDI has its own special type of connector.

Ferrul - A component of a connector that holds a fiber optic cable in place and aids in its alignment. It is usually cylindrical in shape with a hold through the center.

Fiber - Thin filament of glass. An optical waveguide consisting of a core and a cladding which is capable of carrying information in the form of light.

Fiber bandwidth - The lowest frequency at which the magnitude of the fiber transfer function decreases to a specified fraction of the zero frequency value. Often the specified value is ½ of the value of the transfer function at zero frequency.

Fiber bundle - An assembly of unbuffered fiber optic cables. It is usually employed as a single transmission channel. This is in contrast to multi-fiber cables, which contain optically and mechanically isolated fiber optic cables, each of which provides a separate channel. Fiber bundles, which are used only to transmit light as in fiber optic data communications, are flexible and unaligned. On the other hand, fiber bundles which are used to transmit images may be flexible or rigid, but must contain aligned fibers.

Fiber channel - An industry standard specification for computer channel communications over a fiber optic cable. It offers data transmission speeds from 132 MBPS to 1,062 MBPS and transmission distances for 1 to 10 km

Fiber loss - The attenuation (deterioration) of the light signal in transmission through a fiber optic cable.

Fiber Distributed Data Interface network - A token passing ring network designed specifically for fiber optic cable and featuring dual counter-rotating rings and 100 MBPS operation.

Fiber optic interrepeater link - Standard defining a fiber optic cable link between 2 repeaters in an IEEE 802.3 network.

Fiber optic link - Any transmission channel using a fiber optic cable as the transmission medium to connect 2 end terminals or to be connected in series with other channels.

Fiber optics - Light transmission through optical fibers for communication or signaling.

Fiber Optic Test Procedure (FOTP) - Standards developed and published by the Electronic Industries Association (EIA) under the EIA's RS-455 series of standards.

Fiber optic waveguide - A relatively long strand of transparent substance, usually glass, capable of conducting an electromagnetic wave of optical wavelength (visible or near visible region of the frequency spectrum) with some ability to confine longitudinally directed, or near longitudinally directed, lightwaves to its interior by means of internal reflection. The fiber optic waveguide may be homogeneous or radically inhomogeneous with step or graded changes in its refractive index. The indices are lower at the outer regions and the core is thus of an increased refractive index.

FITL - Fiber in the loop.

FM - Frequency modulation.

FO7 - Plastic fiber optic cable connector standardized in Japan.

FOIRL - Fiber optic interrepeater link.

FOTS - Fiber optic transmission system.

F4B/5B Encoding - A signal modulation scheme in which groups of 4 bits are encoded and transmitted in 5 bits in order to guarantee that no more than 3 consecutive zeros ever occur. It is used in FDDI.

FP-LD - Fabry-Perot laser diode.

Frequency modulation - A transmission technique in which the frequency of a carrier is varied in sympathy with the information being communicated.

Fresnel reflection - The reflection that occurs at the planar junction of 2 materials having different refractive indices. Fresnel reflection is not a function of the angle of incidence.

Fresnel reflection loss - Loss of optical power due to Fresnel reflections.

Fundamental mode - The lowest order propagation mode of a waveguide.

Fused coupler - A method of making a multi-mode or single-mode coupler by wrapping fiber optic cables together, heating them and pulling them to form a central unified mass. By doing this light on any input fiber optic cable is coupled to all out put fiber optic cables.

Fusion splicing - A permanent joint accomplished by the application of localized heat sufficient to fuse or melt the ends of the fiber optic cable. This process forms a single continuous fiber optic cable.

Fusion splice - A joining of 2 fiber optic cables by physically fusing through heat the 2 fiber optic cable ends.

FWHM - Full width at half maximum. This is used to describe the width of a spectral emission.