A star coupler is a device that takes in an input signal and splits it into several output signals.

In fiber optics, and especially in telecommunications, a star coupler is a passive optical device, used in network

Telecommunications network

A telecommunications network is a collection of terminals, links and nodes which connect together to enable telecommunication between users of the terminals. Networks may use circuit switching or message switching. Each terminal in the network must have a unique address so messages or connections...

 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, 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.

DEC computers

A star coupler was also the name of a device sold by Digital Equipment Corporation

Digital Equipment Corporation

Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...

 (now part of Hewlett-Packard

Hewlett-Packard

Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...

) of Maynard

Maynard, Massachusetts

Maynard is a town in Middlesex County, Massachusetts, United States. As of the 2010 census, the town population was 10,106.- History :Maynard, located on the Assabet River, was incorporated as an independent municipality in 1871. Prior to that it was known as 'Assabet Village' but was legally...

, Massachusetts

Massachusetts

The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...

. In this case, the star coupler 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 Mb

Megabit

The megabit is a multiple of the unit bit for digital information or computer storage. The prefix mega is defined in the International System of Units as a multiplier of 106 , and therefore...

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

Redundancy (engineering)

In engineering, redundancy is the duplication of critical components or functions of a system with the intention of increasing reliability of the system, usually in the case of a backup or fail-safe....

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

VAX

VAX was an instruction set architecture developed by Digital Equipment Corporation in the mid-1970s. A 32-bit complex instruction set computer ISA, it was designed to extend or replace DEC's various Programmed Data Processor ISAs...

- and later Alpha

DEC Alpha

Alpha, originally known as Alpha AXP, is a 64-bit reduced instruction set computer instruction set architecture developed by Digital Equipment Corporation , designed to replace the 32-bit VAX complex instruction set computer ISA and its implementations. Alpha was implemented in microprocessors...

-based computers running Digital's VMS operating system, to provide a passive, highly reliable interconnect for Digital's cluster technology.