Distance du grand cercleLa distance du grand cercle, également appelée distance orthodromique, est la plus courte distance entre deux points sur une sphère. La surface de la Terre étant approximativement sphérique, la distance du grand cercle est généralement employée pour mesurer la distance entre deux points à sa surface, à partir de leur longitude et leur latitude. R est le rayon de la sphère (le rayon de la Terre vaut environ ). δ est la latitude (en radians). λ est la longitude (en radians). Sur une sphère de rayon R, la dist
Primary sourceIn the study of history as an academic discipline, a primary source (also called an original source) is an artifact, document, diary, manuscript, autobiography, recording, or any other source of information that was created at the time under study. It serves as an original source of information about the topic. Similar definitions can be used in library science and other areas of scholarship, although different fields have somewhat different definitions.
Double-clad fiberDouble-clad fiber (DCF) is a class of optical fiber with a structure consisting of three layers of optical material instead of the usual two. The inner-most layer is called the core. It is surrounded by the inner cladding, which is surrounded by the outer cladding. The three layers are made of materials with different refractive indices. There are two different kinds of double-clad fibers. The first was developed early in optical fiber history with the purpose of engineering the dispersion of optical fibers.
Multi-mode optical fiberMulti-mode optical fiber is a type of optical fiber mostly used for communication over short distances, such as within a building or on a campus. Multi-mode links can be used for data rates up to 100 Gbit/s. Multi-mode fiber has a fairly large core diameter that enables multiple light modes to be propagated and limits the maximum length of a transmission link because of modal dispersion. The standard G.651.1 defines the most widely used forms of multi-mode optical fiber.
Single-mode optical fiberIn fiber-optic communication, a single-mode optical fiber (SMF), also known as fundamental- or mono-mode, is an optical fiber designed to carry only a single mode of light - the transverse mode. Modes are the possible solutions of the Helmholtz equation for waves, which is obtained by combining Maxwell's equations and the boundary conditions. These modes define the way the wave travels through space, i.e. how the wave is distributed in space. Waves can have the same mode but have different frequencies.
Secondary sourceIn scholarship, a secondary source is a document or recording that relates or discusses information originally presented elsewhere. A secondary source contrasts with a primary source, which is an original source of the information being discussed; a primary source can be a person with direct knowledge of a situation or a document created by such a person. A secondary source is one that gives information about a primary source. In this source, the original information is selected, modified and arranged in a suitable format.
