1. In fiber optics, a loss of optical power at a splice or connector, caused by a lateral, i.e., transverse, offset of the mating fiber cores, which offset causes an imperfect transfer of the optical signal from the "transmitting" fiber to the "receiving" fiber.
Note: The effect of a given amount of lateral offset will depend on other parameters such… (Read More →)

1. A partially ordered mathematical set for which every pair of elements has a greater lower bound and a least upper bound [CESG].
Note: A lattice may be used to represent the relationship between security classes. A security clearance specifies the least upper bound of security classes of objects for which access rights may be granted. See also: Dominance.
2.… (Read More →)

1. The angle, with respect to the normal, at which a light ray emerges from a surface.
2. The beam divergence at an emitting surface, such as that of a light-emitting diode (LED), laser, lens, prism, or optical fiber end face.
3. At an end face of an optical fiber, the angle between an input ray and the fiber axis.… (Read More →)

The numerical aperture of an optical system used to couple (launch) power into an optical fiber.
Note 1: LNA may differ from the stated NA of a final focusing element if, for example, that element is underfilled or the focus is other than that for which the element is specified.
Note 2: LNA is one of the parameters that determine… (Read More →)

An optical fiber used in conjunction with a source to excite the modes of another fiber in a particular fashion.
Note: Launching fibers are most often used in test systems to improve the precision of measurements. Synonym injection fiber.

In communications cables--including fiber-optic cables--having the transmission media wrapped helically around a central member, the longitudinal distance along the cable required for one complete helical wrap; i.e., the total cable length divided by the total number of wraps.
Note 1: In many fiber-optic cable designs, the lay length is shorter than in metallic cables of similar diameter, to avoid overstressing… (Read More →)

1. In radio wave propagation, see F region.
2. In telecommunications networks and open systems architecture, a group of related functions that are performed in a given level in a hierarchy of groups of related functions.
Note: In specifying the functions for a given layer, the assumption is made that the specified functions for the layers below are performed, except… (Read More →)

An active element within a layer. [T1.630-1999]

A part of the activity of the layer entities. [T1.627-1993]

The boundary between two adjacent layers in the model. [T1.110-1987]