Abstract: An optical interconnection device suitable for an N.times.N' coupler as used, for example, in a local area network, comprises diffraction means in the form of a body having a refractive index which varies spatially and periodically in one plane of the body. The arrangement is such that light incident upon the body in the plane and at a predetermined angle will be refracted to emerge at a plurality of discrete angles determined by the spatially varying refractive index. The incident light is distributed substantially equally among the plurality of output refracted beams and substantially all of said incident light is coupled to the plurality of refracted beams. The diffraction means comprises a cylindrical body, and the device further comprises two arrays of optical sources and/or receivers. The arrays are disposed at opposite faces, respectively, of the body, each of the optical receivers having an optical axis aligned with one of the discrete angles.