Optical tee coupler for data bus system with single multimode fibres

A new type of optical tee coupler was developed for a data bus system with single multimode fibres. It is constructed of a wedge-shaped mirror and three graded-index rod lenses. Its three ports, which are ready to plug in, interconnect asymmetrically with one another. For a laser diode of wavelength 0.9 ¿m, the coupling losses between three fibres attached into the ports were adjusted to be 3.9 to 7.9 dB. The coupler insertion losses were 1.3 to 2.5 dB.