Coupler for optical communication system

Claim 1

In an optical communication system having at least three optical signal transmission lines each comprising at least one optical waveguide having a core of transparent material having a refractive index n1 surrounded by a layer of transparent cladding material having a refractive index n2 that is lower than n1, a coupler for coupling the signal in any one of said optical transmission lines to all of the remaining optical transmission lines, said coupler comprising an elongated rod of transparent material of refractive index n3 having an outer side surface and first and second planar endfaces that are substantially perpendicular to the longitudinal axis thereof, the length L of said rod satisfying the equation L > OR = d/2 tan c where d is the diameter of said rod and the angle c is the acceptance half angle of said at least one optical waveguide, means surrounding said rod and cooperating with said outer side surface thereof for forming an interface for reflecting back into said rod light from said transmissiOn lines that impinges upon said side surface, means disposed on said second endface for reflecting light, the wavelength of which is to be transmitted by said optical signal transmission lines, and support means for disposing the ends of said optical signal transmission lines in a bundled, parallel arrangement, the optical waveguides of which said transmission lines are comprised terminating in faces that are disposed in a substantially planar array adjacent to said first endface.