Coupler for optical communication system

Claim 1

An optical coupler for connecting optical signal transmission lines in an optical communication system, such that an optical signal in anyone of the lines of a first group of lines is transmitted to all other lines of a second group, each of said lines comprising at least one optical waveguide, said coupler comprising: a propagation medium having a revolution shape about an optical propagation axis and including first and second planar endfaces substantially perpendicular to said axis; at least one optical mixer in the form of an elongated cylindrically shaped rod having first and second planar and parallel faces, said first face constituting said first endface; first and second elongated rods in the shape of truncated cones forming a biconical structure each having parallel and planar faces namely a major base and a minor base and being united end to end by their minor bases which are identical, said first frusto-conical rod being further united by its major base to said second face of said optical rod mixer whose cross-section corresponds to the associated major base; layer means surrounding said propagation medium except said planar endfaces for reflecting light that impinges upon the peripheral surface thereof; and support means for connecting said transmission lines to said endfaces respectively such that the optical waveguides of which a group of transmission lines is comprised terminate parallel to the said optical propagation axis with waveguide endfaces disposed in a plane substantially adjacent to the corresponding endface; the diameters of said bases and axial length of said bi-conical structure being determined to provide a substantially hemispherical radiation pattern at said minor bases no matter what is the direction of the optical propagation along said axis, given the numerical aperture value of each of the associated group of transmission lines.