|
Submarine Branching Unit
A submarine branching unit is a piece of equipment used in submarine telecommunications cable systems to allow the cable to split to serve more than one destination. For example, one branch might head for a cable landing point and others may continue. There are several methods by which the split can be affected, which can also depend on the type of cable system: * Purely electrical systems (now almost obsolete) can be split by either: ** Physically separating the signal cables so some go in one direction and some in another, which requires no additional power. ** Using an add-drop multiplexer to direct the signals down one path or the other. The electrical equipment that acts as the add-drop multiplexer will need powering. * Optical fibre cable systems can be split by either: ** Physically separating the signal-carrying fibres so some go in one direction and some in another, which requires no additional power. ** Converting the optically carried signals to electrical signals, using ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Submarine Communications Cable
A submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean and sea. The first submarine communications cables laid beginning in the 1850s carried telegraphy traffic, establishing the first instant telecommunications links between continents, such as the first transatlantic telegraph cable which became operational on 16 August 1858. Subsequent generations of cables carried telephone traffic, then data communications traffic. Modern cables use optical fibre technology to carry digital data, which includes telephone, Internet and private data traffic. Modern cables are typically about in diameter and weigh around for the deep-sea sections which comprise the majority of the run, although larger and heavier cables are used for shallow-water sections near shore. Submarine cables first connected all the world's continents (except Antarctica) when Java was connected to Darwin, Northern Terri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cable Landing Point
A cable landing point is the location where a submarine or other underwater cable makes landfall. The term is most often used for the landfall points of submarine telecommunications cables and submarine power cables. The landing will either be direct (in the case of a point-to-point cable system) or via a branch from a main cable using a submarine branching unit. The branch can be several kilometres long. Selection criteria Cable landing points are usually carefully chosen to be in areas: # that have little marine traffic to minimise the risk of cables being damaged by ship anchors and trawler operations; # with gently sloping, sandy or silty sea-floors so that the cable can be buried to minimise the chance of damage; # without strong currents that would uncover buried cables and potentially move cables. Such locations are rare, and will usually be the shared landfall point for several cable systems. Associated facilities Frequently, there will be a nearby cable landing s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Add-drop Multiplexer
An add-drop multiplexer (ADM) is an important element of an optical fiber network. A multiplexer combines, or multiplexes, several lower-bandwidth streams of data into a single beam of light. An ''add-drop'' multiplexer also has the capability to ''add'' one or more lower-bandwidth signals to an existing high-bandwidth data stream, and at the same time can extract or ''drop'' other low-bandwidth signals, removing them from the stream and redirecting them to some other network path. This is used as a local "on-ramp" and "off-ramp" to the high-speed network. ADMs can be used both in long-haul core networks and in shorter-distance " metro" networks, although the former are much more expensive due to the difficulty of scaling the technology to the high data rates and dense wavelength division multiplexing (DWDM) used for long-haul communications. The main optical filtering technology used in add-drop multiplexers is the Fabry–Pérot etalon. Newer "multi-service SONET/SDH" (a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reconfigurable Optical Add-drop Multiplexer
In fiber optics, a reconfigurable optical add-drop multiplexer (ROADM) is a form of optical add-drop multiplexer that adds the ability to remotely switch traffic from a wavelength-division multiplexing (WDM) system at the wavelength layer. This is achieved through the use of a wavelength selective switching module. This allows individual or multiple wavelengths carrying data channels to be added and/or dropped from a transport fiber without the need to convert the signals on all of the WDM channels to electronic signals and back again to optical signals. The main advantages of the ROADM are: * The planning of entire bandwidth assignment need not be carried out during initial deployment of a system. The configuration can be done as and when required without affecting traffic already passing the ROADM. * ROADM allows for remote configuration and reconfiguration. * In ROADM, as it is not clear beforehand where a signal can be potentially routed, there is a necessity of power balancing o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equilateral Triangle
In geometry, an equilateral triangle is a triangle in which all three sides have the same length. In the familiar Euclidean geometry, an equilateral triangle is also equiangular; that is, all three internal angles are also congruent to each other and are each 60°. It is also a regular polygon, so it is also referred to as a regular triangle. Principal properties Denoting the common length of the sides of the equilateral triangle as a, we can determine using the Pythagorean theorem that: *The area is A=\frac a^2, *The perimeter is p=3a\,\! *The radius of the circumscribed circle is R = \frac *The radius of the inscribed circle is r=\frac a or r=\frac *The geometric center of the triangle is the center of the circumscribed and inscribed circles *The altitude (height) from any side is h=\frac a Denoting the radius of the circumscribed circle as ''R'', we can determine using trigonometry that: *The area of the triangle is \mathrm=\fracR^2 Many of these quantities have simple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Festoon Cable
A festoon (from French ''feston'', Italian ''festone'', from a Late Latin ''festo'', originally a festal garland, Latin ''festum'', feast) is a wreath or garland hanging from two points, and in architecture typically a carved ornament depicting conventional arrangement of flowers, foliage or fruit bound together and suspended by ribbons. The motif is sometimes known as a swag when depicting fabric or linen.Sturgis, pp. 22-23 In modern English the verb forms, especially "festooned with", are often used very loosely or figuratively to mean having any type of fancy decoration or covering. Origins and design Its origin is probably due to the representation in stone of the garlands of natural flowers, etc., which were hung up over an entrance doorway on fête days, or suspended around an altar. The design was largely employed both by the Ancient Greeks and Romans and formed the principal decoration of altars, friezes and panels. The ends of the ribbons are sometimes formed into ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
