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
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 ...
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
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 capabili ...
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 an add-drop multiplexer to divide and recombine the signals on the desired paths, the reconverting back to optically carried signals. This signal conversion and multiplexing equipment will require power.
** Using a
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 a ...
to direct optical carrier frequencies down desired paths. The power requirements of optical multiplexing in this manner will be lower than the previous method.
In both types of cable system, more than one technique can be used simultaneously.
The conventional symbol used for a submarine branching unit in maps of cable routes is a small
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 othe ...
with (usually) one vertex pointing towards the top of the map.
See also
*
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 depicti ...
References
* (404 on 11 Oct 2013)
{{DEFAULTSORT:Submarine Branching Unit
Submarine communications cables