- Industry: Telecommunications
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The region where the angular field distribution is essentially independent of distance from the source. Note 1: If the source has a maximum overall dimension D that is large compared to the wavelength, the far-field region is commonly taken to exist at distances greater than 2D2/ from the source, being the wavelength. Note 2: For a beam focused at infinity, the far-field region is sometimes referred to as the Fraunhofer region. Synonyms far field, far zone, Fraunhofer region, radiation field.
Industry:Telecommunications
The region of the electromagnetic spectrum that can be perceived by human vision, approximately the wavelength range of 0. 4 m to 0. 7 m.
Industry:Telecommunications
The region of the electromagnetic spectrum bounded by the long-wavelength extreme of the visible spectrum (approximately 0. 7 m) and the shortest microwaves (approximately 0. 1 mm. ) See electromagnetic spectrum.
Industry:Telecommunications
The region between two curves, such as circles or rectangles, used to specify the tolerance on component size and geometry. 2. Pertaining to the cross section of an optical fiber, when used to specify the respective diameters and ovalities of, and concentricity error between, the core and cladding; two concentric annular regions which define the core-cladding boundary and the cladding outer boundary. Note: Dimensions are usually expressed in micrometers (m. ) The larger annular region is defined by concentric circles of diameter and , where DC is the nominal diameter of the cladding and DC is the cladding diameter tolerance. The smaller annular region is defined by concentric circles of diameter and , where Dc is the nominal diameter of the core and Dc is the core diameter tolerance. When the core and cladding boundaries of the cross section of the fiber in question fall entirely within their respective defined areas, the fiber meets the specification. 3. Of the cross section of a given optical fiber, when used to characterize the respective diameters and ovalities of the core and cladding, and the concentricity error between the core and cladding; two such pairs of concentric circles, the concentric pairs not necessarily being concentric with one another. Note 1: One pair of concentric circles characterizes the core, and the other pair, the cladding. The cladding ovality is characterized by the smallest circle that circumscribes its cross section, and the largest circle that fits within its cross section. (The cross section is assumed, to a first approximation, to be elliptical in shape, so these defining circles will be concentric. ) The core cross section is characterized by an analogous pair of circles, also concentric with one another, but not necessarily with those defining the cladding cross section. Note 2: The distance between the centers of the two concentric pairs (core pair and cladding pair) defines the offset between the core and cladding (the "core-cladding offset,"also called the "concentricity error". ) The width of the annulus defined by the cladding circles determines the ovality of the cladding, and the width of the annulus defined by the core determines the ovality of the core.
Industry:Telecommunications
The regeneration of a display to show current status, based on changes to the previously displayed data. Note: An update can be accomplished upon user request or by automatic means.
Industry:Telecommunications
The refractive index of the Earth's atmosphere, calculated from observations of pressure, temperature, and humidity at the surface of the Earth. Note: The surface refractivity gradient is the difference in refractive index between the surface and a given altitude, such as between the surface and 1000 m.
Industry:Telecommunications
The reflection that occurs when light, in a higher refractive-index medium, strikes an interface, with a medium with a lower refractive index, at an angle of incidence (with respect to the normal) greater than the critical angle. See Snell's law (Note 3. )
Industry:Telecommunications
The reflectance at the surface of a material so thick that the reflectance does not change with increasing thickness, i.e., the intrinsic reflectance of the surface, irrespective of other parameters such as the reflectance of the rear surface. Note: The term "reflectivity" is no longer in common use. See reflectance.
Industry:Telecommunications
The reduction of the number of data elements, bandwidth, cost, and time for the generation, transmission, and storage of data without loss of information by eliminating unnecessary redundancy, removing irrelevancy, or using special coding. Note 1: Examples of data compaction methods are the use of fixed-tolerance bands, variable-tolerance bands, slope-keypoints, sample changes, curve patterns, curve fitting, variable-precision coding, frequency analysis, and probability analysis. Note 2: Simply squeezing noncompacted data into a smaller space, for example by increasing packing density or by transferring data on punched cards onto magnetic tape, is not data compaction. Note 3: Whereas data compaction reduces the amount of data used to represent a given amount of information, data compression does not.
Industry:Telecommunications
The reduction of the bandwidth needed to transmit a given amount of data in a given time. 2. The reduction of the time needed to transmit a given amount of data in a given bandwidth. Note: Bandwidth compression implies a reduction in normal bandwidth of an information-carrying signal without reducing the information content of the signal.
Industry:Telecommunications
