Star couplers are optocouplers in which an incoming light signal is divided in a star shape among several optical fibers. There are several different methods for splitting a light signal in a star shape onto several optical fibers.
One star coupler method is based on twisting and fusing multiple fibers, similar to what is done in the two-fiber biconical taper coupler. Another method uses diffused glass that is mirrored at one end face. The light signal is coupled in at one end face, refracted in the diffuse glass, reflected at the mirror at the other end face, and coupled out into the other fibers. The attenuation of the light is correspondingly high. A third method uses a diffused glass platelet into which mode-guidingchannels are diffused and through which light energy is coupled in and out. These couplers are characterized by having low light losses.
Star couplers are used as central components for star-shaped optical fiber networks. It connects numerous transmitters and receivers and distributes the signal power supplied by a connected transmitter evenly to all connected receivers. Optical star couplers are available as active components with an electrical repeater or as passive components.
The principle is that there is one outgoing and one return lightwave line from each of the connected stations. Light arriving on an input line is collected and distributed to all return lines by a scattering process. In this process, a synchronization of the transmitters must be carried out on a higher layer so that only one station is transmitting at a time. The methods usually used for LANs are basically suitable for this purpose. Each optical star coupler supports only a limited number of connections (e.g. 32), since the design has its technical limits here. Active couplers can be cascaded from one end of the network to the other as required, taking into account a maximum runtime.