A star coupler is a device that takes in an input

signal A signal is both the process and the result of transmission of data over some media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processing, information theory and biology. In ...

and splits it into several output signals. In

fiber optics An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can transmit light from one end to the other. Such fibers find wide usage in fiber-optic communications, where they permit transmission over longer distances and at ...

, and especially in

telecommunications Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...

, a star coupler is a passive optical device, used in

network Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

applications. An optical signal introduced into any input port is distributed to all output ports. Because of the way a passive star coupler is constructed, the number of ports is usually a power of 2; i.e., two input ports and two output ports (a "two-port" coupler, customarily called a ''

directional coupler Power dividers (also power splitters and, when used in reverse, power combiners) and directional couplers are passive devices used mostly in the field of radio technology. They couple a defined amount of the electromagnetic power in a transmiss ...

,'' or ''splitter''); four input ports and four output ports (a "four-port" coupler); eight input ports and eight output ports (an "eight-port" coupler), etc.

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president until ...

(now part of

Hewlett-Packard The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company. It was founded by Bill Hewlett and David Packard in 1939 in a one-car garage in Palo Alto, California ...

) of

Maynard, Massachusetts Maynard is a town in Middlesex County, Massachusetts, United States. The town is located 22 miles west of Boston, in the MetroWest and Greater Boston region of Massachusetts and borders Acton, Concord, Stow and Sudbury. The town's populatio ...

sold a star coupler that interconnected links to computers via coaxial cable rather than optical fibres, but the function was essentially the same. The signal that was distributed was 70

Mbit The bit is the most basic unit of information in computing and digital communication. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represented as ...

/s computer interconnect (CI) data and the star coupler provided two

redundant Redundancy or redundant may refer to: Language * Redundancy (linguistics), information that is expressed more than once Engineering and computer science * Data redundancy, database systems which have a field that is repeated in two or more table ...

paths of either 8 or 16 ports each. Digital's star coupler was developed for use with the

VAX VAX (an acronym for virtual address extension) is a series of computers featuring a 32-bit instruction set architecture (ISA) and virtual memory that was developed and sold by Digital Equipment Corporation (DEC) in the late 20th century. The V ...

- and later

Alpha Alpha (uppercase , lowercase ) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter ''aleph'' , whose name comes from the West Semitic word for ' ...

-based computers running Digital's

OpenVMS OpenVMS, often referred to as just VMS, is a multi-user, multiprocessing and virtual memory-based operating system. It is designed to support time-sharing, batch processing, transaction processing and workstation applications. Customers using Op ...

operating system, to provide a passive, highly reliable interconnect for Digital's

cluster may refer to: Science and technology Astronomy * Cluster (spacecraft), constellation of four European Space Agency spacecraft * Cluster II (spacecraft), a European Space Agency mission to study the magnetosphere * Asteroid cluster, a small ...

technology.

References

* * FAA Glossary of Optical Communications Terms {{telecom-stub Telecommunications equipment DEC hardware